Triple-Output Power Supply with Fault Protection MAX1889 provides

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Triple-Output Power Supply with Fault Protection MAX1889 provides

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19-2485; 7/02
Triple-Output Power Supply with Fault Protection
MAX1889 provides three regulated output voltages required active matrix, thin-film transistor liquid crystal displays (TFT LCDs). combines high-performance step-up regulator with linear-regulator controllers multiple levels protection circuitry complete power-supply system. main DC-DC converter high-frequency (500kHz/1MHz), current-mode step-up regulator with integrated N-channel power MOSFET that allows ultra-small inductors ceramic capacitors. With high closed-loop bandwidth performance, MAX1889 provides fast transient response pulsed loads while operating with efficiencies over 85%. positive negative linear-regulator controllers postregulate charge-pump outputs gate-on gate-off supplies. MAX1889 unique input switch control that replace typical input fuse disconnecting load from input supply when fault detected. fault detector monitors three regulated output voltages monitor current from input supply well. Additionally, MAX1889 enters thermal shutdown when overtemperature threshold reached. MAX1889 undervoltage lockout 2.5V (max) allow input supply droop under pulsed load conditions while avoiding unexpected behavior when input voltage dips momentarily. Also, builtin soft-start cycle-by-cycle current limiting prevent input surge currents during power-up. MAX1889 available 16-pin package with maximum thickness 1.0mm ultra-thin panel design.
Features
High-Performance Step-Up Regulator Fast Transient Response Current-Mode Control Architecture Built-In High-Efficiency N-Channel Power MOSFET Current-Limit Comparator >85% Efficiency Selectable Switching Frequency (500kHz/1MHz) Internal Soft-Start Positive Linear-Regulator Controller Negative Linear-Regulator Controller Triple-Level Protection Against Smoke Fire Input Switch Replaces Input Fuse Output Overload Detection with Timer Latch Thermal Shutdown 2.7V 5.5V Input Operating Range Ultra-Small External Components Shutdown Current (max) Quiescent Current (max) Ultra-Thin 16-Pin Package (1mm Maximum Thickness)
MAX1889
Ordering Information
PART MAX1889EGE TEMP RANGE -40°C +85°C PIN-PACKAGE (5mm 5mm)
Applications
Notebook Computer Displays Navigation Displays
Configuration
TGND FREQ DRVN DRVP
VIEW
SHDN PGND
MAX1889
Typical Operating Circuit appears data sheet.
Maxim Integrated Products
GATE
Monitors
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Triple-Output Power Supply with Fault Protection MAX1889
ABSOLUTE MAXIMUM RATINGS
SHDN, OCN, OCP, FBP, FBN, FREQ .-0.3V PGND GND.±0.3V PGND .-0.3V +14V DRVP .-0.3V +30V REF, GATE, TGND .-0.3V (VIN 0.3V) DRVN .(VIN 28V) (VIN 0.3V) Continuous Power Dissipation +70°C) 16-Pin (derate 19.2mW/°C above +70°C) .1538mW Operating Temperature Range MAX1889EGE .-40°C +85°C Junction Temperature .+150°C Storage Temperature.-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN SHDN CREF 0.22µF, PGND GND, +85°C. Typical values +25°C, unless otherwise noted.)
PARAMETER Supply Range Undervoltage Lockout (UVLO) Threshold Quiescent Current Shutdown Current Output Voltage Thermal Shutdown MAIN STEP-UP REGULATOR Main Output Voltage Range Operating Frequency Oscillator Maximum Duty Cycle Regulation Voltage Fault Trip Level Load Regulation Line Regulation Input Bias Current Switch On-Resistance Leakage Current Current Limit Current Rating Soft-Start Period Soft-Start Step Size POSITIVE LINEAR-REGULATOR CONTROLLER Regulation Voltage Fault Trip Level Input Bias Current Effective Transconductance IFBP VFBP IDRVP 0.2mA VFBP falling VFBP 1.25V VDRVP 10V, IDRVP 0.1mA 1.213 0.96 1.25 1.288 1.04 RLX(ON) ILIM tested 4096 fOSC VREF 200mA, slope (Note falling IMAIN full load 2.7V 5.5V 1.5V -100 0.01 VMAIN fOSC VFREQ VFREQ 1.229 0.95 0.85 1.242 -1.6 +100 1.254 1.05 1.15 VREF SYMBOL VUVLO 350mV typical hysteresis SHDN -2µA IREF 50µA 1.231 rising falling CONDITIONS 2.55 2.35 1.250 2.85 1.269 UNITS
VFBP 1.5V, VFBN (Note
Triple-Output Power Supply with Fault Protection
ELECTRICAL CHARACTERISTICS (continued)
(VIN SHDN CREF 0.22µF, PGND GND, +85°C. Typical values +25°C, unless otherwise noted.)
PARAMETER Line Regulation Bandwidth DRVP Sink Current DRVP Off-Leakage Current Regulation Voltage Fault Trip Level Input Bias Current Effective Transconductance Line Regulation Bandwidth DRVN Sink Current DRVN Off-Leakage Current LOGIC SIGNAL (SHDN) Input Voltage Input High Voltage Input Current LOGIC SIGNAL (FREQ) Input Voltage Input High Voltage Input Current OVERCURRENT COMPARATOR Input Offset Voltage Input Bias Current OCN, Input Common-Mode Range FAULT TIMER GATE DRIVER Fault Timer Period GATE Output Sink Current During Slew GATE Output Pulldown Resistance GATE Output Pullup Resistance tFAULT IGATE VFREQ 32768/fOSC VFREQ VIN, 65536/fOSC VGATE 1.5V, during turn-on transition VGATE 0.5V IOCN, IOCP VOCN VOCP IFREQ 0.15 typical hysteresis 0.01 SHDN 100mV typical hysteresis, 2.7V 5.5V 2.7V 5.5V 0.01 IDRVN IFBN VFBN IDRVP SYMBOL (Note VFBP 1.1V, VDRVP VFBP 1.1V, VDRVP IDRVN 0.2mA VFBN rising VFBN VDRVN -10V, IDRVN 0.1mA IDRVN 0.2mA, 2.7V 5.5V (Note VFBN 200mV, VDRVN -10V VFBP -0.1V, VDRVN -20V CONDITIONS IDRVP 0.2mA, 2.7V 5.5V UNITS
MAX1889
NEGATIVE LINEAR-REGULATOR CONTROLLER
Triple-Output Power Supply with Fault Protection MAX1889
ELECTRICAL CHARACTERISTICS
(VIN SHDN CREF 0.22µF, PGND GND, -40°C +85°C.) (Note
PARAMETER Supply Range ULVO Threshold Quiescent Current Shutdown Current Output Voltage MAIN STEP-UP REGULATOR Main Output Voltage Range Operating Frequency Oscillator Maximum Duty Cycle Regulation Voltage Fault Trip Level Line Regulation Input Bias Current Switch On-Resistance Current Limit Regulation Voltage Fault Trip Level Input Bias Current Effective Transconductance Bandwidth DRVP Sink Current Regulation Voltage Fault Trip Level Input Bias Current Effective Transconductance Bandwidth DRVN Sink Current LOGIC SIGNAL (SHDN) Input Voltage Input High Voltage Input Current ISHDN 100mV typical hysteresis IDRVN IFBN IDRVP VFBN IFBP RLX(ON) ILIM VFBP IDRVP 0.2mA VFBP falling VFBP 1.25V VDRVP 10V, IDRVP 0.1mA (Note VFBP 1.1V, VDRVP IDRVN 0.2mA VFBN rising VFBN VDRVN -10V, IDRVN 0.1mA (Note VFBN 200mV, VDRVN -10V 1.213 0.96 200mA, slope (Note falling 2.7V 5.5V 1.5V -100 VMAIN fOSC VFREQ 0.75 1.215 0.96 1.25 1.260 1.04 0.45 +100 1.288 1.04 VREF SYMBOL VUVLO rising falling VFBP 1.5V, VFBN (Note SHDN -2µA IREF 50µA 1.231 CONDITIONS 2.55 2.85 1.269 UNITS
POSITIVE LINEAR-REGULATOR CONTROLLER
NEGATIVE LINEAR-REGULATOR CONTROLLER
Triple-Output Power Supply with Fault Protection
ELECTRICAL CHARACTERISTICS (continued)
(VIN SHDN CREF 0.22µF, PGND GND, -40°C +85°C.) (Note
PARAMETER LOGIC SIGNAL (FREQ) Input Voltage Input High Voltage Input Current OVERCURRENT COMPARATOR Input Offset Voltage Input Bias Current OCN, Input Common-Mode Range FAULT TIMER GATE DRIVER GATE Output Sink Current GATE Output Pulldown Resistance GATE Output Pullup Resistance IGATE VGATE 1.5V, during turn-on transition VGATE 0.5V IOCN, IOCP VOCN VOCP IFREQ 0.15 typical hysteresis SYMBOL CONDITIONS UNITS
MAX1889
Note Quiescent current does include switching losses. Note regulation voltage tested with slope compensation ramp. Slope compensation needs included when selecting resisitors setting output voltage (see Main Step-Up Regulator Output Voltage Selection sections). Note Guaranteed design. production tested. Note Specifications -40°C guaranteed design, production tested.
Typical Operating Characteristics
(Circuit Figure +3.3V, VMAIN +9V, +20V, -7V, SHDN FREQ PGND GND, +25°C, unless otherwise noted.)
STEP-UP REGULATOR EFFICENCY LOAD CURRENT (VMAIN
MAX1889 toc01
MAX1889 toc02
EFFICIENCY
OUTPUT VOLTAGE 2.7V 3.3V 5.5V
EFFICIENCY
2.7V 3.3V 5.5V 1000
2.7V 3.3V 5.5V 1000
LOAD CURRENT (mA)
1000 LOAD CURRENT (mA)
LOAD CURRENT (mA)
MAX1889 toc03
STEP-UP REGULATOR OUTPUT VOLTAGE LOAD CURRENT (VMAIN
STEP-UP REGULATOR EFFICIENCY LOAD CURRENT (VMAIN 13V)
Triple-Output Power Supply with Fault Protection MAX1889
Typical Operating Characteristics (continued)
(Circuit Figure +3.3V, VMAIN +9V, +20V, -7V, SHDN FREQ PGND GND, +25°C, unless otherwise noted.)
STEP-UP REGULATOR OUTPUT VOLTAGE LOAD CURRENT (VMAIN 13V)
MAX1889 toc04
STEP-UP REGULATOR SWITCHING FREQUENCY INPUT VOLTAGE
MAX1889 toc05
STEP-UP REGULATOR LOAD-TRANSIENT RESPONSE 200mA)
MAX1889 toc06
13.1 13.0 OUTPUT VOLTAGE 12.9 12.8 12.7 5.5V 12.6 12.5 2.7V 3.3V
1100 1000 FREQUENCY (kHz) 3.3V VMAIN IMAIN 200mA
500mA
8.9V 200mA
1000 10µs/div INDUCTOR CURRENT, 500mA/div VMAIN 100mV/div, AC-COUPLED IMAIN 200mA, 200mA/div LOAD CURRENT (mA) INPUT VOLTAGE
STEP-UP REGULATOR LOAD-TRANSIENT RESPONSE PULSE)
MAX1889 toc07
STEP-UP REGULATOR SOFT-START (10mA LOAD) FROM SLOW-RISING INPUT SUPPLY
MAX1889 toc08
STEP-UP REGULATOR SOFT-START (200mA LOAD) FROM SLOW-RISING INPUT SUPPLY
MAX1889 toc09
8.9V 8.8V 10µs/div INDUCTOR CURRENT, 1A/div VMAIN 100mV/div, AC-COUPLED IMAIN 1A/div 1ms/div VIN, 5V/div VGATE, 5V/div VC2, 5V/div VMAIN 5V/div
1ms/div VIN, 5V/div VGATE, 5V/div VC2, 5V/div VMAIN 5V/div
Triple-Output Power Supply with Fault Protection
Typical Operating Characteristics (continued)
(Circuit Figure +3.3V, VMAIN +9V, +20V, -7V, SHDN FREQ PGND GND, +25°C, unless otherwise noted.)
MAX1889
POWER-UP SEQUENCE FROM SLOW-RISING INPUT SUPPLY
MAX1889 toc10
STEP-UP REGULATOR SOFT-START (10mA LOAD) USING SHDN CONTROL
MAX1889 toc11
STEP-UP REGULATOR SOFT-START (200mA LOAD) USING SHDN CONTROL
MAX1889 toc12
1ms/div VSHDN, 5V/div VGATE, 5V/div VC2, 5V/div VMAIN 5V/div
1ms/div VSHDN, 5V/div VGATE, 5V/div VC2, 5V/div VMAIN 5V/div
2ms/div VIN, 5V/div VMAIN 5V/div 20V, 10V/div -7V, 10V/div
-10V
POWER-UP SEQUENCE USING SHDN CONTROL
MAX1889 toc13
STEP-UP REGULATOR NORMAL OPERATION (200mA LOAD)
MAX1889 toc14
POSITIVE CHARGE-PUMP OUTPUT VOLTAGE LOAD CURRENT
MAX1889 toc15
26.2 OUTPUT VOLTAGE 9.05V 26.0 25.8 25.6 25.4 25.2 25.0
2ms/div VSHDN, 5V/div VMAIN 5V/div 20V, 10V/div -7V, 10V/div -10V 1µs/div VLX, 5V/div VMAIN 50mV/div, AC-COUPLED INDUCTOR CURRENT, 500mA/div
500mA
3.3V IMAIN 200mA LOAD CURRENT (mA)
Triple-Output Power Supply with Fault Protection MAX1889
Typical Operating Characteristics (continued)
(Circuit Figure +3.3V, VMAIN +9V, +20V, -7V, SHDN FREQ PGND GND, +25°C, unless otherwise noted.)
POSITIVE CHARGE-PUMP INCREMENTAL EFFICIENCY LOAD CURRENT
MAX1889 toc16
NEGATIVE CHARGE-PUMP OUTPUT VOLTAGE LOAD CURRENT
MAX1889 toc17
NEGATIVE CHARGE-PUMP INCREMENTAL EFFICIENCY LOAD CURRENT
EFFICIENCY
MAX1889 toc18
EFFICIENCY LOAD CURRENT (mA) (VOUT IOUT) (PIN(LOAD) PIN(NOLOAD))
-8.2
-8.3 OUTPUT VOLTAGE
-8.4
-8.5
-8.6 3.3V IMAIN 200mA -8.7 LOAD CURRENT (mA)
(VOUT IOUT) (PIN(LOAD) PIN(NOLOAD)) LOAD CURRENT (mA)
POSITIVE LINEAR-REGULATOR LOAD REGULATION
MAX1889 toc19
POSITIVE LINEAR-REGULATOR LOAD-TRANSIENT RESPONSE
MAX1889 toc20
NEGATIVE LINEAR-REGULATOR LOAD REGULATION
MAX1889 toc21
OUTPUT VOLTAGE VARIATION
OUTPUT VOLTAGE VARIATION
-0.03
-0.08
-0.06
19.95V
-0.16
-0.09 10mA -0.15 LOAD CURRENT (mA) 2ms/div 20V, 50mV/div, AC-COUPLED 10mA, 10mA/div
-0.24
-0.12
-0.32
-0.40 LOAD CURRENT (mA)
Triple-Output Power Supply with Fault Protection
Typical Operating Characteristics (continued)
(Circuit Figure +3.3V, VMAIN +9V, +20V, -7V, SHDN FREQ PGND GND, +25°C, unless otherwise noted.)
MAX1889
NEGATIVE LINEAR-REGULATOR LOAD-TRANSIENT RESPONSE
MAX1889 toc22
OVERCURRENT PROTECTION RESPONSE OVERLOAD DURING STARTUP
MAX1889 toc23
OVERCURRENT PROTECTION RESPONSE OVERLOAD DURING NORMAL OPERATION
MAX1889 toc24
-6.95V
-10mA 400µs/div -7V, 50mV/div, AC-COUPLED -10mA, 10mA/div 20ms/div VGATE, 5V/div VMAIN, 5V/div; IMAIN 1.5A VPL, 10V/div; 10mA VNL, 10V/div; 10mA -10V 20ms/div VGATE, 5V/div VMAIN 5V/div; IMAIN 200mA 1.5A 20V, 10V/div; 10mA -7V, 10V/div; 10mA -10V
REFERENCE VOLTAGE LOAD CURRENT
MAX1889 toc25
CURRENT LIMIT INPUT VOLTAGE
MAX1889 toc26
1.250
REFERENCE VOLTAGE
1.249
1.248 CURRENT LIMIT
1.247
1.246
1.245 LOAD CURRENT (µA)
INPUT VOLTAGE
Triple-Output Power Supply with Fault Protection MAX1889
Description
NAME SHDN FUNCTION Active-Low Shutdown Control Input. Pull SHDN below 0.4V logic-low level turn sections device pull GATE high. Pull SHDN above 1.6V logic-high level enable device. leave SHDN floating. Power Ground. PGND source N-channel power MOSFET. Connect PGND analog ground (GND) device's pins. Analog Ground. Connect power ground (PGND) device's pins. Internal Reference Bypass Terminal. Connect 0.22µF ceramic capacitor from analog ground (GND). External load capability least 50µA. Main Step-Up Regulator Feedback Input. regulates 1.25V nominal. Connect center resistive voltage-divider between main output (VMAIN) analog ground (GND) main step-up regulator output voltage. Place resistive voltage-divider close pin. Negative Linear-Regulator Feedback Input. regulates 125mV nominal. Connect center resistive voltage-divider between negative output (VNEG) negative linear-regulator output voltage. Place resistive voltage-divider close pin. Negative Linear-Regulator Base Drive. Open drain internal P-channel MOSFET. Connect DRVN base external linear-regulator pass transistor (see Pass Transistor Selection section). Positive Linear-Regulator Base Drive. Open drain internal N-channel MOSFET. Connect DRVP base external linear-regulator pass transistor (see Pass Transistor Selection section). Positive Linear-Regulator Feedback Input. regulates 1.25V nominal. Connect center resistive voltage-divider between positive output (VPOS) analog ground (GND) positive linear-regulator output voltage. Place resistive voltage-divider close pin. Frequency Select Input. Pull FREQ above logic-high level (0.7 VIN) frequency 1MHz pull FREQ below logic-low level (0.3 VIN) frequency 500kHz. leave FREQ floating. Switching Node. Drain internal N-channel power MOSFET main step-up regulator. Internal connection. Connect this ground. Overcurrent Comparator Inverting Input. connects center resistive voltagedivider connected drain input protection P-channel MOSFET (see Input Overcurrent Protection section). unused, connect REF. Overcurrent Comparator Noninverting Input. connected center resistive voltage-divider that sets input overcurrent threshold (see Input Overcurrent Protection section). unused, connect GND. Gate Driver Output External P-Channel MOSFET (see Input Overcurrent Protection section). unused, leave GATE open. Supply Input. supply voltage powers control circuitry. input voltage range from 2.7V 5.5V. Bypass with 0.1µF ceramic capacitor between GND, close pins possible.
PGND
DRVN
DRVP
FREQ TGND
GATE
Triple-Output Power Supply with Fault Protection MAX1889
VMAIN
2.7V 5.5V
3.3µF 6.3V 3.3µF 6.3V
4.7µH 43.2k 150k GATE
4.7µF 4.7µF 4.7µF
51.1k 0.47µF
1000pF 100pF
0.01µF
150k
12.1k
220pF
TGND
SHDN
0.22µF
FREQ
MAX1889
PGND
0.1µF 0.1µF
0.1µF
2200pF 470pF
0.15µF
0.15µF
0.1µF
150k 24.3k
DRVN
DRVP
301k
+20V
1000pF
1000pF EXTERNAL LOGIC SIGNAL (ENABLE LOW)
OPTIONAL 221k VMAIN OPTIONAL EXTERNAL LOGIC SIGNAL (ENABLE LOW)
ANALOG GROUND (GND)
POWER GROUND (PGND)
Figure Standard Application Circuit
Triple-Output Power Supply with Fault Protection MAX1889
SHDN
FREQ
REFERENCE 1.25V REFOK
GATE DRIVER
GATE
2.70V 2.35V
OVERCURRENT COMPARATOR OSCILLATOR SLOPE_COMP
UVLO COMPARATOR
VMAIN ONMN SEQUENCE FAULT DETECTOR FAULMAIN STEP-UP WITH SOFT-START PGND
THERMAL SHUTDOWN SSDONE
DRVP
ANALOG GAIN BLOCK
FAULT COMPARATOR
MAX1889 0.35V 0.125V
ANALOG GAIN BLOCK
DRVN
FAULT COMPARATOR
Figure MAX1889 System Functional Diagram
Triple-Output Power Supply with Fault Protection
Table Component List
DESIGNATION DESCRIPTION 3.3µF, 6.3V ceramic capacitors (0805) Taiyo Yuden JMK212BJ335MG 4.7µF, ceramic capacitors (1210) Taiyo Yuden LMK352BJ475MF 1.0A, Schottky diode (S-flat) Toshiba CRS02 200mA, dual-series Schottky diodes (SOT23) Fairchild BAT54S 250mA, switching diode (SOT23) Central Semiconductor CMPD914 6.8µH, 1.3A inductor Coilcraft LPO2506IB-682 2.4A, P-channel MOSFET (3-pin SuperSOT) Fairchild FDN304P 200mA, bipolar transistor (SOT23) Fairchild MMBT3904 200mA, bipolar transistor (SOT23) Fairchild MMBT3906
Detailed Description
MAX1889 contains high-performance, step-up switching regulator, low-cost linear-regulator controllers, multiple levels protection circuitry. Figure shows system functional diagram device. output voltage main step-up converter (VMAIN) from with external resistive voltage-divider. high switching frequency (500kH/1MHz) main step-up converter current-mode control provide fast transient response allow lowprofile inductors ceramic capacitors. internal power MOSFET minimizes external component count while achieving high efficiency incorporating lossless current-sensing technology. switching node (LX) generate both positive negative voltage supplies driving charge-pump stages capacitors diodes. user many charge-pump stages needed generate supply voltages more than +30V -15V. positive negative linear-regulator controllers postregulate charge-pump supply voltages allow users program power-up sequencing well. unique input switch control MAX1889 senses current drawn from input power supply monitoring voltage drop across input P-channel MOSFET latches overcurrent condition lasts more than fault timer period. addition, three outputs monitored fault conditions that last longer than fault latch timer. junction temperature exceeds +160°C, device goes into latched shutdown state.
MAX1889
Standard Application Circuit
standard application circuit (Figure MAX1889 generates +9V, +20V, outputs displays. input voltage from 2.7V 5.5V. Table lists recommended component options Table lists component suppliers.
Main Step-Up Regulator
main step-up regulator switches 1MHz 500kHz) employs current-mode control architecture maximize loop bandwidth provide fast-transient response pulsed loads found source drivers panels. Also, high switching frequency allows low-profile inductors capacitors minimize thickness panel designs. integrated high-efficiency MOSFET IC's built-in soft-start function reduce number external components required while controlling inrush current.
Table Component Suppliers
SUPPLIER Coilcraft Fairchild Taiyo Yuden Toshiba PHONE 847-639-6400 408-822-2000 800-348-2496 949-455-2000 847-639-1469 408-822-2102 847-925-0899 949-859-3963 WEBSITE www.coilcraft.com www.fairchildsemi.com www.t-yuden.com www.toshiba.com
Triple-Output Power Supply with Fault Protection MAX1889
Depending input-to-output voltage ratio, regulator controls output voltage power delivered output modulating duty cycle power MOSFET each switching cycle. duty cycle MOSFET approximated MAIN VMAIN rising edge internal clock, controller sets flip-flop, which turns N-channel MOSFET (Figure input voltage applied across inductor. inductor current ramps linearly, storing energy magnetic field. Once feedback voltage error-amplifier output, slope-compensation, current-feedback signals trip multi-input comparator, MOSFET turns off, flipflop resets. Since inductor current continuous, transverse potential develops across inductor that turns diode (D1). voltage across inductor becomes difference between output voltage input voltage. This discharge condition forces current through inductor ramp back down, transferring energy output capacitor load. MOSFET remains rest clock cycle.
RESET DOMINANT PGND ILIM COMPARATOR
MAX1889
ILIM CURRENT SENSE
FAULT
SLOPE_COMP
REFOUT SOFT-START SSOK
REFIN
ONMN
SSDONE
Figure Main Step-Up Regulator Functional Diagram
Triple-Output Power Supply with Fault Protection
Positive Linear-Regulator Controller
positive linear regulator provides positive high voltage gate drivers. high voltage produced using charge-pump circuit shown Figure many stages necessary obtain required output voltage (see Selecting Number Charge-Pump Stages section). positive linear-regulator controller analog gain block with open-drain N-channel output. drives external pass transistor with base-to-emitter resistor post-regulate charge-pump output (Figure regulator controller designed stable with output capacitor 0.1µF more. enable regulator using external control signal, apply logic-control input series with signal diode (Figure Additional delay added with external circuitry. Note that voltage rating DRVP output 28V. higher voltages present, external cascode transistor should used with emitter connected DRVP, base VMAIN, collector base PNP. (Figure regulator controller designed stable with output capacitor 0.1µF more. negative linear regulator enabled soon main step-up regulator enabled. enable regulator using external control signal, apply logic-control input through open-drain output N-channel MOSFET (Figure Additional delay added with external circuitry (see Applications Information section). Note that voltage rating DRVN output 28V. higher voltages present, external cascode transistor should used with emitter connected DRVN, base GND, collector base NPN.
MAX1889
Undervoltage Lockout (UVLO)
UVLO comparator MAX1889 compares input voltage with UVLO threshold (2.7V rising, 2.35V falling, typ) ensure that input voltage high enough reliable operation. 350mV (typ) hysteresis prevents supply transients from causing restart. Once input voltage exceeds UVLO threshold, controller enables reference block. Once reference above 1.05V, internal 12µA current source pulls GATE turns external P-channel MOSFET switch (P1, Figure that connects input supply regulator. When input voltage falls below UVLO threshold, controller sets fault latch pulls GATE high with internal switch turn quickly (Figure
Negative Linear-Regulator Controller
negative linear regulator provides negative voltage required supply gate drivers panels. negative voltage produced using charge pump circuit shown Figure many stages necessary obtain required output voltage (see Selecting Number Charge-Pump Stages section). negative linear-regulator controller analog gain block with open-drain P-channel output. drives external pass transistor with baseto-emitter resistor postregulate charge-pump out-
Reference Voltage (REF)
reference output nominally 1.25V, source least 50µA (see Typical Operating Characteristics). Bypass with 0.22µF ceramic capacitor connected between GND.
Oscillator Frequency (FREQ)
internal oscillator frequency programmable. Connect FREQ ground 500kHz operation 1MHz operation. Note that soft-start period scales with oscillator frequency (see Soft-Start section).
GATE
Shutdown (SHDN)
0.625V
12µA
logic-low signal SHDN disables device functions including reference. When shut down, supply current drops 0.1µA (typ) maximize battery life. output capacitance, feedback resistors, load current determine rate which each output voltage decays. logic-high signal SHDN activates MAX1889 (see Power-Up Sequencing section). leave floating. unused, connect SHDN Toggling SHDN cycling clears fault latch.
Figure External Input P-Channel MOSFET Switch Control
Triple-Output Power Supply with Fault Protection MAX1889
Power-Up Sequencing Inrush Current Control
Once SHDN high, MAX1889 enables UVLO circuitry compares input voltage with UVLO rising threshold (2.7V, typ). input voltage exceeds UVLO rising threshold, reference enabled. When reference voltage ramps above 1.05V (typ), MAX1889 enables oscillator turns external P-channel MOSFET (Figure pulling GATE low. GATE pulled down with 12µA current source. capacitor from gate drain slow down turn-on rate MOSFET, reduce inrush current. Once GATE reaches around 0.6V, internal N-channel MOSFET turns pulls GATE ground order maximize enhancement external P-channel MOSFET. fully turns main step-up regulator powers with soft-start (see Soft-Start section). negative linear regulator enabled same time main step-up regulator. positive linear regulator enabled after soft-start routine completed. fault detection timer begins after main step-up regulator finished soft-start period.
Input Overcurrent Protection
high-side overcurrent comparator MAX1889 provides input overcurrent protection when used together with external P-channel MOSFET switch (Figure Connect resistive voltage-dividers from source drain overcurrent threshold. center taps dividers connected overcurrent comparator inputs (OCN OCP) Setting Input Overcurrent Threshold section information calculating resistor values. overcurrent event activates fault-protection circuitry.
Fault Protection
Once soft-start routine completed, output main regulator either linear regulator below respective fault-detection threshold, input overcurrent comparator pulls high, MAX1889 activates fault timer. fault condition still exists after 64ms fault-timer duration, MAX1889 sets fault latch, which shuts down outputs except reference, which remains active. After removing fault condition, toggle SHDN (below 0.4V) cycle input voltage (below 2.2V) clear fault latch reactivate device.
Soft-Start
soft-start main step-up regulator (Figure achieved ramping reference voltage multi-input comparator 4096 oscillator clock cycles. 4096 clock cycles correspond 4.096ms 1MHz operation 8.192ms 500kHz operation. reference comparator comes from 5-bit that generates steps when reference ramps from final value. This soft-start method allows gradual increase output voltage reduce input surge current (see startup waveforms Typical Operating Characteristics). average input current given COUT MAIN where VMAIN main step-up regulator output voltage, input voltage, COUT main step-up regulator output capacitor, efficiency step-up regulator, soft-start period (4.096ms 1MHz operation 8.192ms 500kHz operation).
Thermal Shutdown
thermal shutdown feature limits total power dissipation MAX1889. When junction temperature (TJ) exceeds +160°C, thermal sensor sets fault latch (Figure which shuts down outputs except reference, allowing device cool down. Once device cools down 15°C, toggle SHDN (below 0.4V) cycle input voltage (below 2.2V) clear fault latch reactivate device.
Design Procedure
Main Step-Up Regulator
Output Voltage Selection Adjust output voltage connecting resistive voltage-divider from output (VMAIN) with center connected (Figure Select range. Calculate with following equations: (VMAIN where
1.242V 20mV)
VMAIN VMAIN
example, VMAIN 0.66, 1.229V. VMAIN range from 13V.
Triple-Output Power Supply with Fault Protection
Inductor Selection minimum inductance value, peak current rating, series resistance, size factors consider when selecting inductor. These factors influence converter's efficiency, maximum output load capability, transient response time, output voltage ripple. most applications, values between 3.3µH 20µH work best with MAX1889's switching frequencies. maximum load current, input voltage, output voltage, switching frequency determine inductor value. given load current, higher inductor value results lower peak current and, thus, less output ripple, degrades transient response possibly increases size inductor. equations provided here include constant defined LIR, which ratio peak-to-peak inductor current ripple average inductor current. good compromise between size inductor, power loss, output voltage ripple, select 0.5. inductance value then given IN(TYP) MAIN
power loss inductor's series resistance (PLR) approximated following equation: I(LAVG)2RL MAIN MAIN where IL(AVG) average inductor current inductor's series resistance. best performance, select inductors with resistance less than internal N-channel MOSFET's on-resistance (0.25 typ). minimize radiated noise sensitive applications, shielded inductor. Output Capacitor output capacitor affects circuit stability output voltage ripple. 10µF ceramic capacitor works well most applications. Depending output capacitor chosen, feedback compensation required desirable increase loop-phase margin increase loop bandwidth transient response (see Feedback Compensation section). total output voltage ripple components: capacitive ripple caused charging discharging output capacitance, ripple capacitor's equivalent series resistance (ESR): VRIPPLE VRIPPLE(ESR) VRIPPLE(C) VRIPPLE(ESR) IPEAKRESR(COUT), VRIPPLE(C) MAIN MAIN COUT VMAINfOSC where IPEAK peak inductor current (see Inductor Selection section). ceramic capacitors, output voltage ripple typically dominated VRIPPLE(C). voltage rating temperature characteristics output capacitor must also considered. Step-Up Regulator Compensation loop stability current-mode step-up regulator analyzed using small-signal model. continuous conduction mode (CCM), loop-gain transfer function consists dominant pole, high-frequency pole, right-half-plane (RHP) zero, zero. case ceramic output capacitors, zero very high frequency.
MAX1889
MAIN VIN(TYP) MAIN(MAX)fOSC
where efficiency, fOSC oscillator frequency (see Electrical Characteristics), IMAIN includes primary load current input supply currents charge pumps. Considering typical application circuit, maximum average load current (IMAIN(MAX)) 200mA with output. Based above equations, assuming efficiency switching frequency 1MHz, inductance value 9.4µH 0.3. inductance value 5.6µH 0.5. inductance standard application circuit chosen 6.8µH. inductor's peak current rating should higher than peak inductor current throughout normal operating range. peak inductor current given MAIN(MAX)VMAIN IPEAK VIN(MIN) Under fault conditions, inductor current reach internal current limit (see Electrical Characteristics). However, soft saturation inductors controller's fast current-limit circuitry protect device from failure during such fault condition. inductor's resistance significantly affect efficiency conduction losses inductor.
Triple-Output Power Supply with Fault Protection MAX1889
Therefore, dominant pole zero determine loop response step-up regulator. frequency dominant pole DOMINANT 2RLC zero-pole pair loop connecting network from main output (lead compensation). frequencies pole zero compensation are:
where load resistance output capacitor. frequency zero
where duty cycle, inductance, gain given 20log where internal current-sense resistor, feedback divider resistors Figure However, adding lead compensation (Figure useful adjust trade-off between stability transient response. greater phase margin needed stability, lower bandwidth acceptable, pole-zero pair connecting network from ground (lag compensation). Conversely, higher bandwidth required faster transient response, lower phase margin acceptable,
frequencies zero pole lead compensation are:
VMAIN
compensation resistors change gain affecting loop bandwidth phase margin crossover. Reducing bandwidth much compensation) harms transient response, while increasing much harms phase margin stability. rule, start with approximately equal half R2). typical application, compensation capacitors range between 100pF 1000pF. Then, check stability monitoring transient response waveform when pulsed load applied output. Using Compensation Improved Soft-Start digital soft-start main step-up regulator limits average input current during startup. order smooth each step digital soft-start, lowfrequency lead compensation network (Figure network effectively spreads switching pulses lowers peak inductor currents. smoothing network active only during soft-start when output voltage rises. Positive changes output instantaneously coupled through feed-forward capacitor This arrangement generates smoothly rising output voltage. When output voltage reaches regulation, charges through turns off. most applications, lead compensation needed disabled making large. With pole zero compensation network very close another cancel out.
MAX1889
PGND
Figure External Compensation
Triple-Output Power Supply with Fault Protection
Input Capacitor input capacitor (CIN) reduces current peaks drawn from input supply reduces noise injection into device. 3.3µF ceramic capacitors used standard application circuit (Figure because high source impedance seen typical setups. Actual applications usually have much lower source impedance since step-up regulator typically runs directly from output another regulated supply. Typically, reduced below values used standard applications circuit. Ensure noise supply using adequate CIN. Alternatively, greater voltage variation tolerated decoupled from using lowpass filter (see Figure Rectifier Diode MAX1889's high switching frequency demands high-speed rectifier. Schottky diodes recommended most applications because their fast recovery time forward voltage. general, Schottky diode complements internal MOSFET well. Input P-Channel MOSFET Select input P-channel MOSFET based current rating, voltage rating, gate threshold, on-resistance. MOSFET must able handle peak input current (see Inductor Selection section). drain-to-source voltage rating input MOSFET should higher than maximum input voltage. Because MOSFET conducts full input current, on-resistance should enough higher efficiency. low-threshold MOSFET ensure that switch fully enhanced lowest input voltages. Setting Input Overcurrent Threshold high-side comparator MAX1889 provides input overcurrent protection when used conjunction with external P-channel MOSFET accuracy overcurrent threshold affected many factors, including comparator offset, resistor tolerance, input voltage range, variations MOSFET DS(ON) input overcurrent comparator only intended protect against catastrophic failures. This function similar input fuse. minimize impact comparator's input offset current-sense accuracy, sense voltage should close upper limit common-mode range, which extends input voltage. resistive voltage-divider (R3/R4), combined with on-state resistance sets overcurrent threshold. center R3/R4 connected inverting input (OCN) shown Figure comparator resistors ideal, threshold current where both inputs equal: IL(MAX) RDS(MAX)
MAX1889
IL(MAX) average inductor current maximum load condition minimum input voltage, given IL(MAX) VOUT VIN(MIN) ILOAD(MAX)
where efficiency main step-up regulator. step-up regulator's minimum input voltage 2.7V, output voltage maximum load current 0.3A. Assuming efficiency, maximum average inductor current IL(MAX) 0.3A 1.25A 2.7V DS(MAX) maximum on-state drain-to-source resistance maximum RDS(ON) +25°C found MOSFET data sheet, that number does include temperature coefficient. Since temperature coefficient resistance 0.5%/°C, RDS(MAX) calculated with following equation: RDS(MAX) 25°C 0.005
where actual MOSFET junction temperature normal operation ambient temperature rise self-heating caused power dissipation. example, consider Fairchild FDN304P, which maximum RDS(ON) room temperature 70m.
RDS(ON)
COMP
Figure Setting Overcurrent Threshold
Triple-Output Power Supply with Fault Protection MAX1889
junction temperature +100°C, maximum onstate resistance overtemperature RDS(MAX) 0.005 (100 100m given values, ideal ratio R3/R4 determined: IPEAK(MAX) RDS(MAX) consider effect resistor tolerance, comparator offset, input voltage variation, minimum threshold equation
VIN(MIN)
RDS(TYP) VIN(TYP)
following example shows apply above equations design. resistors used, then 0.01. VOCP around VIN, select 51.1k 150k. Assume that minimum input voltage 2.7V typical input voltage 3.3V, average inductor current maximum load 1.25A, maximum RDS(ON) 100m:
0.01 0.9802 0.01
(VIN(MIN) IL(MAX) RDS(MAX)
where VIN(MIN) minimum expected value input voltage, tolerance resistors worst-case input offset voltage comparator. simplify equation, define constant follows:
2.7V 1.25A 0.9802 150k 0.005V 2.7V 150k 0.9802 51.1k 0.2637
=150k, then 39.2k. typical overcurrent threshold 150k (39.2k 150k) 3.3V 0.047 150k (51.1k 150k)
4.15A
minimum threshold equation becomes: VIN(MIN)
Charge Pumps
Selecting Number Charge-Pump Stages highest efficiency, always choose lowest number charge-pump stages that meets output requirement. number positive charge-pump stages given VDROPOUT VMAIN NPOS VMAIN where NPOS number positive charge-pump stages, positive linear-regulator output, VMAIN main step-up regulator output, forward voltage drop charge-pump diode, VDROPOUT dropout margin linear regulator. VDROPOUT
(VIN(MIN) IL(MAX) RDS(MAX)
Solving R3/R4 yields: VIN(MIN) IL(MAX) RDS(MAX) VIN(MIN) R3/R4 ratio guarantees required minimum level IL(MAX). typical overcurrent threshold given
Triple-Output Power Supply with Fault Protection
number negative charge-pump stages given NNEG -VNL VDOPOUT VMAIN output voltage ripple dominated capacitance value. following equation approximate required capacitor value: COUT ILOAD 2fOSCVRIPPLE
MAX1889
where NNEG number negative charge-pump stages, negative linear-regulator output, VMAIN main step-up regulator output, forward voltage drop charge-pump diode, VDROPOUT dropout margin linear regulator. VDROPOUT above equations derived based assumption that first stage positive charge pump connected VMAIN first stage negative charge pump connected ground. Sometimes fractional stages more desirable better efficiency. This done connecting first stage another available supply. first charge-pump stage powered from VIN, then above equations become: VDROPOUT NPOS VMAIN VDROPOUT NNEG VMAIN Flying Capacitor Increasing flying capacitor (CX) value increases output current capability. Increasing capacitance indefinitely negligible effect output current capability because internal switch resistance diode impedance limit source impedance. 0.1µF ceramic capacitor works well most low-current applications. flying capacitor's voltage rating must exceed following: VMAIN where stage number which flying capacitor appears, VMAIN main output voltage. example, two-stage positive charge pump typical application circuit (Figure where VMAIN contains flying capacitors. flying capacitor first stage (C14) requires voltage rating over flying capacitor second stage (C13) requires voltage rating over 18V. Charge-Pump Output Capacitor Increasing output capacitance decreasing reduces output ripple voltage peak-topeak transient voltage. With ceramic capacitors,
where VRIPPLE peak-to-peak value output ripple. Charge-Pump Rectifier Diodes Schottky diodes with current rating equal greater than times average charge-pump input current.
Linear-Regulator Controllers
Output Voltage Selection Adjust positive linear-regulator output voltage connecting resistive voltage-divider from with center connected (Figure Select range 30k. Calculate with following equation: [(VPL VFBP) where VFBP 1.25V. Adjust negative linear-regulator output voltage connecting resistive voltage-divider from with center connected (Figure Select range 30k. Calculate with following equation: [(VFBN VNL) (VREF VFBN)] where VFBN 125mV, VREF 1.25V. Note that only guaranteed source 50µA. Using resistor less than results higher bias current than supply. Connecting another resistor (R14) from VMAIN (Figure solve this problem because main output supply part resistor's (R10) bias current. following equation determine value R14: VMAIN VREF VREF VFBN 40µA
Drawing only 40µA from leaves remaining 10µA other purposes. Pass Transistor Selection pass transistor must meet specifications current gain input capacitance, collector-emitter saturation voltage, power dissipation.
Triple-Output Power Supply with Fault Protection MAX1889
transistor's current gain limits guaranteed maximum output current ILOAD(MAX) IDRV where IDRV minimum base-drive current, pullup resistor connected between transistor's base emitter. Furthermore, transistor's current gain increases linear regulator's loop gain (see Stability Requirements section), excessive gain destabilizes output. Therefore, transistors with current gain over maximum output current recommended. transistor's input capacitance input resistance also create second pole, which could enough make output unstable when heavily loaded. transistor's saturation voltage maximum output current determines minimum input-to-output voltage differential that linear regulator supports. Alternatively, package's power dissipation could limit usable maximum input-to-output voltage differential. maximum power dissipation capability transistor's package mounting must exceed actual power dissipation device. power dissipation equals maximum load current times maximum input-to-output voltage differential: ILOAD(MAX) (VLDOIN VLDOOUT ILOAD(MAX)VCE During startup, outputs below their respective setpoints, base drive pass transistors maximum. large drive currents cause charge-pump outputs collapse. chargepump loading objectionable, base resistors added between drive outputs (DRVN DRVP) pass transistors (Figure These resistors limit maximum drive current prevent discharging charge pump's output capacitors. Select minimum base drive current meet maximum required output current: IDRIVE(MIN) ILDOOUT(MAX)
resistance required guarantee this base current RBASE VLDOIN(MAX) IDRIVE(MIN) VLDOIN(MAX) ILDOOUT(MAX)
consequence adding base resistors, voltage change DRVN DRVP accompanies changes drive current. This voltage change coupled through parasitic capacitance feedback pins. rate voltage change sufficiently large, cause instability.
2200pF 470pF
MAX1889
DRVN
DRVP
Figure Limiting Drive Current During Startup
Triple-Output Power Supply with Fault Protection MAX1889
avoid excessive voltage coupling, small capacitor added parallel with base resistor. resulting time constant should between 50µs. Stability Requirements MAX1889 linear-regulator controllers internal transconductance amplifier drive external pass transistor. transconductance amplifier, pass transistor, base-emitter resistor, output capacitor determine loop stability. output capacitor pass transistor properly selected, linear regulator unstable. transconductance amplifier regulates output voltage controlling pass transistor's base current. total loop gain approximately: BIAShFE AV(LDO) ILOAD where 26mV room temperature, IBIAS current through base-to-emitter resistor (RBE). This bias resistor typically providing 0.23mA current, biasing near regulation voltage setpoint. output capacitor load resistance create dominant pole system. pass transistor's input capacitance creates second pole system. Additionally, output capacitor's generates zero. achieve stable operation, following equations verify that linear regulator properly compensated: First, determine dominant pole linear regulator's output capacitor load resistor: fPOLE(CLDO) 2CLDORLOAD ILOAD(MAX) 2CLDO VLDO third pole linear regulator's feedback resistance capacitance (including stray capacitance) between (for positive LDO) (for negative LDO) (Figure fPOLE(FB)_ fPOLE(FB)_ 2CFB (R12II R13) 2CFB (R9II R10)
second third poles occur well after unitygain crossover, linear regulator remains stable: fPOLE(CBE) 2fPOLE(CLDO) AV(LDO) However, zero occurs before unity-gain crossover, cancel zero with feedback pole changing circuit components such that: fPOLE(FB) 2COUTRESR
most applications where ceramic capacitors used, zero always occurs after crossover. capacitor connected between output feedback node improves transient response, reduces noise coupled into feedback loop, maintains correct regulation point (Figure Output Capacitor Selection Typically, more output capacitance provides best solution, since this also reduces output voltage drop immediately after load transient. Connect least 0.1µF capacitor between linear regulator's output ground, close external pass transistor possible. Depending selected pass transistor, larger capacitor values required stability (see Stability Requirements section). Furthermore, output capacitor's affects stability. output capacitors with less than 200m ensure stability optimum transient response. Once minimum capacitor value stability determined, verify that linear regulator's output does contain excessive noise. Although adequate stability, small capacitor values provide much bandwidth, making linear regulator sensitive noise. Larger capacitor values reduce bandwidth, thereby reducing regulator's noise sensitivity. noise ground reference causes design marginally stable negative linear regulator, bypass negative output back reference voltage. This technique reduces differential noise output.
unity gain crossover linear regulator fCROSSOVER AV(LDO) fPOLE(CLDO) Next, determine second pole baseto-emitter capacitance (including transistor's input capacitance), transistor's input resistance, base-to-emitter pullup resistor: fPOLE(CBE) 2CBE (RBE VThFE LOAD 2CBERBE VThFE
Triple-Output Power Supply with Fault Protection MAX1889
Applications Information
Board Layout
Careful board layout extremely important proper operation. following guidelines good board layout: Minimize area high-current loops placing input capacitors, inductor, output diode, output capacitors less than 0.2in (5mm) from PGND pins. Connect these components with traces wide possible. Avoid using vias high-current paths. vias unavoidable, many vias parallel reduce resistance inductance. Create islands analog ground (GND), power ground (PGND), linear regulator ground. Starconnect them backside device. bypass capacitor both feedback dividers should connected analog ground island (GND). step-up regulator's input output capacitors, charge-pump components should wide power ground plane. power ground plane should connected power ground (PGND) with wide trace. Maximizing width power ground traces improves efficiency reduces output voltage ripple noise spikes. other ground connections, such bypass capacitor linear regulator output capacitors, should star-connected backside device with wide traces. Make other connections between these separate ground planes. Place bypass capacitors close device possible. Place feedback voltage-divider resistors close their respective feedback pins possible. divider's center trace should kept short. Placing resistors away causes their traces become antennas that pick switching noise. Care should taken avoid running feedback trace near switching nodes charge pumps. Minimize length maximize width traces between output capacitors load best transient responses. Minimize size node while keeping wide short. Keep node away from feedback nodes (FB, FBP, FBN) analog ground. traces shield necessary. Refer MAX1889 evaluation example proper board layout.
MAX1889
150k
DRVN
DRVP
301k
1000pF
1000pF
24.3k
Figure Compensation
Triple-Output Power Supply with Fault Protection
Additional Application Circuits
Operation with Output Voltage >13V maximum output voltage step-up regulator 13V, which limited absolute maximum rating internal power MOSFET. achieve higher output voltage, external N-channel MOSFET cascoded with internal (Figure Since gate external biased from input supply, logic-level ensure that fully enhanced minimum input voltage. current rating needs higher than internal current limit. Changing Power-Up Sequence power-up sequencing linear regulators controlled using external delays. Figure shows application where negative linear-regulator output powers with certain delay after positive linear regulator reaches regulation. resistors capacitor form network that provides power-up delay. time constant this network
MAX1889
VMAIN
STEP-UP REGULATOR
PGND
MAX1889
Select ratio that: With this R1/R2 ratio, power-up delay calculated 0.125V where forward voltage drop diode 0.125V regulation point. design example, assume positive linear-regulator output +20V, negative charge-pump output -9V, required power-up delay time 4ms: ratio should9be:
Figure Operation with Output Voltage >13V Using Cascoded MOSFET
required time constant 1.68ms 0.125 Choose 0.1µF, then R1//R2 16.8k. standard resistor values: 24k. Disabling Input MOSFET Switch input protection MOSFET needed, disable input overcurrent comparator connecting ground, Leave GATE floating (Figure 11). Generating Gamma Reference Voltage reference voltage Gamma correction resistor string produced using linear-regulator controller. voltage difference between main boost voltage (VMAIN) Gamma reference voltage 400mV greater, emitter pass transistor should connected VMAIN.
Triple-Output Power Supply with Fault Protection MAX1889
STEP-UP REGULATOR
VMAIN
PGND DRVN NEGATIVE REGULATOR
MAX1889
DRVP POSITIVE REGULATOR
+20V
Figure Controlling Power-Up Sequence with External Delay
voltage difference less than 400mV, then emitter should connected high supply voltage. output charge-pump stages added VMAIN. emitter connected output first stage shown Figure higher efficiency, first charge-pump stage connected rather than VMAIN, this reduces power loss.
Chip Information
TRANSISTOR COUNT: 2396 PROCESS: BiCMOS
Triple-Output Power Supply with Fault Protection MAX1889
3.3V GATE SWITCH CONTROL STEP-UP REGULATOR
VMAIN
PGND
MAX1889
Figure Disabling Input Protection MOSFET Switch
Triple-Output Power Supply with Fault Protection MAX1889
STEP-UP REGULATOR
VMAIN
PGND DRVN
NEGATIVE REGULATOR
MAX1889
DRVP POSITIVE REGULATOR VGAMMA +8.9V
Figure Generating Gamma Reference Voltage
Triple-Output Power Supply with Fault Protection
Package Information
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.) .EPS
MAX1889
Triple-Output Power Supply with Fault Protection MAX1889
Package Information (continued)
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2002 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

Triple-Output Power Supply with Fault Protection MAX1889 provides

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