Internal Switch Bias Supply SOT23 MAX1605 boost converter contain

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Internal Switch Bias Supply SOT23 MAX1605 boost converter contain

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19-1666; 7/00
Internal Switch Bias Supply SOT23
MAX1605 boost converter contains 0.5A internal switch tiny 6-pin SOT23 package. operates from +2.4V +5.5V supply voltage boost battery voltages 0.8V output. MAX1605 uses unique control scheme providing highest efficiency over wide range load conditions. internal 0.5A MOSFET reduces external component count, high switching frequency 500kHz) allows tiny surface-mount components. current limit 500mA, 250mA, 125mA, allowing user reduce output ripple component size low-current applications. Additional features include quiescent supply current shutdown mode save power. MAX1605 ideal small panels with current requirements also used other applications. MAX1605EVKIT evaluation kit) available help speed design time. Adjustable Output Voltage 20mA from Single Battery Efficiency 500kHz Switching Frequency Selectable Inductor Current Limit (125mA, 250mA, 500mA) 18µA Operating Supply Current 0.1µA Shutdown Current Small 6-Pin SOT23 Package
Features
MAX1605
_Applications
Bias Generators Cellular Cordless Phones Palmtop Computers Personal Digital Assistants (PDAs) Organizers Handy Terminals
PART MAX1605EUT-T
Ordering Information
TEMP. RANGE -40°C +85°C PINPACKAGE SOT23-6 MARK AAHP
Typical Operating Circuit
0.8V VOUT 10µH
Configuration
VIEW
SHDN
2.4V 5.5V
VOUT MAX1605
MAX1605
SHDN
SOT23-6
Maxim Integrated Products
free samples latest literature, visit www.maxim-ic.com phone 1-800-998-8800. small orders, phone 1-800-835-8769.
Internal Switch Bias Supply SOT23 MAX1605
ABSOLUTE MAXIMUM RATINGS
VCC, LIM, SHDN GND.-0.3V .-0.3V +30V Continuous Power Dissipation +70°C) 6-Pin SOT23 (derate 8.7mW/°C above +70°C) .696mW Operating Temperature Range .-40°C +85°C Junction Temperature .+150°C Storage Temperature Range .-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
(VCC SHDN 3.3V, +85°C, unless otherwise noted. Typical values +25°C.) (Note
PARAMETER Supply Voltage Inductor Input Voltage Range Undervoltage Lockout Quiescent Supply Current Shutdown Supply Current Line Regulation Line Regulation Load Regulation Efficiency Feedback Point Feedback Input Bias Current Voltage Range Switch Current Limit ILX(MAX) floating On-Resistance Leakage Current Maximum On-Time Minimum Off-Time CONTROL INPUTS SHDN Input Threshold SHDN Input Bias Current ISHDN 2.4V 5.5V 5.5V, SHDN 5.5V 2.4V 5.5V tOFF 1.1V 0.8V (soft-start) 100mA 3.3V, 100mA 0.40 0.20 0.10 0.50 0.25 0.125 0.56 0.285 0.15 1.3V VLNR VLNR VLDR SYMBOL VUVLO (Note (Note falling, 50mV typical hysteresis 1.3V SHDN VOUT 18V, ILOAD 1mA, VLIM 2.4V 5.5V VOUT 18V, ILOAD 1mA, VLIM 2.4V VOUT 18V, VLIM ILOAD 20mA 100µH, 3.6V, ILOAD 10mA 1.225 CONDITIONS 0.15 1.25 1.275 VOUT 2.37 UNITS %/mA
Internal Switch Bias Supply SOT23 MAX1605
ELECTRICAL CHARACTERISTICS (continued)
(VCC SHDN 3.3V, +85°C, unless otherwise noted. Typical values +25°C.) (Note
PARAMETER Input Level Input Float Level Input High Level Input Bias Current ILIM SYMBOL CONDITIONS 2.4V 5.5V 2.4V 5.5V, ILIM ±0.5µA 2.4V 5.5V SHDN VCC, SHDN (VCC 0.2V 0.4V (VCC 0.2V UNITS
ELECTRICAL CHARACTERISTICS
(VCC SHDN 3.3V, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER Supply Voltage Inductor Input Voltage Range Undervoltage Lockout Quiescent Supply Current Shutdown Supply Current Feedback Point Feedback Input Bias Current Voltage Range Switch Current Limit On-Resistance Leakage Current Maximum On-Time Minimum Off-Time CONTROL INPUTS SHDN Input Threshold SHDN Input Bias Current ISHDN 2.4V 5.5V 5.5V, VSHDN 5.5V 2.4V 5.5V tOFF 1.1V 0.8V ILX(MAX) floating 3.3V, 100mA 0.75 0.35 0.18 0.08 0.58 0.30 0.17 1.25 1.3V SYMBOL VUVLO (Note (Note falling, 50mV typical hysteresis 1.3V SHDN 1.215 CONDITIONS VOUT 2.37 1.285 UNITS
Internal Switch Bias Supply SOT23 MAX1605
ELECTRICAL CHARACTERISTICS (continued)
(VCC SHDN 3.3V, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER Input Level Input Float Level Input High Level Input Bias Current ILIM SYMBOL CONDITIONS 2.4V 5.5V 2.4V 5.5V, ILIM ±0.5µA 2.4V 5.5V SHDN VCC, SHDN (VCC 0.25V 0.4V (VCC 0.25V UNITS
Note devices 100% tested +25°C. limits over temperature range guaranteed design. Note MAX1605 requires supply voltage between +2.4V +5.5V; however, input voltage used power inductor vary from +0.8V VOUT.
Typical Operating Characteristics
(VCC 3.3V, 3.6V, 10µH, SHDN VCC, VOUT(NOM) (Figure +25°C, unless otherwise noted.)
OUTPUT VOLTAGE LOAD CURRENT
MAX1605 toc02
OUTPUT VOLTAGE SUPPLY VOLTAGE
3.6V (500mA) IOUT
MAX1605 toc01
OUTPUT VOLTAGE INPUT VOLTAGE
21.5 21.3 21.1 OUTPUT VOLTAGE 20.9 20.7 20.5 20.3 20.1 19.9 19.7 3.3V (500mA) INPUT VOLTAGE IOUT IOUT 18.4 18.3 18.2 OUTPUT VOLTAGE 18.1 18.0 17.9 17.8 17.7 17.6 17.5 17.4 (125mA)
18.1 OUTPUT VOLTAGE 18.0 17.9 17.8 17.7 17.6
(500mA)
IOUT
OPEN (250mA)
19.5 SUPPLY VOLTAGE
LOAD CURRENT (mA)
EFFICIENCY SUPPLY VOLTAGE 10µH)
MAX1605 toc04
EFFICIENCY INPUT VOLTAGE 10µH)
IOUT EFFICIENCY 3.3V ILIM 500mA INPUT VOLTAGE IOUT
MAX1605 toc05
EFFICIENCY LOAD CURRENT 10µH)
EFFICIENCY LOAD CURRENT (mA) (500mA) OPEN (250mA) (125mA)
MAX1605 toc06
IOUT IOUT 10mA
EFFICIENCY
IOUT 3.6V ILIM 500mA
SUPPLY VOLTAGE
MAX1605 toc03
18.2
Internal Switch Bias Supply SOT23
Typical Operating Characteristics (continued)
(VCC 3.3V, 3.6V, 10µH, SHDN VCC, VOUT(NOM) (Figure +25°C, unless otherwise noted.)
EFFICIENCY LOAD CURRENT 47µH)
MAX1605 toc07
MAX1605
EFFICIENCY LOAD CURRENT 100µH)
MAX1605 toc08
CURRENT LIMIT SUPPLY VOLTAGE
CURRENT LIMIT (mA)
MAX1605 toc09
EFFICIENCY (500mA) OPEN (250mA) (125mA)
EFFICIENCY (500mA) (125mA) OPEN (250mA)
OPEN
LOAD CURRENT (mA)
LOAD CURRENT (mA)
SUPPLY VOLTAGE
CURRENT LIMIT INPUT VOLTAGE
MAX1605 toc10
SUPPLY CURRENT SUPPLY VOLTAGE LOAD)
MAX1605 toc11
SUPPLY CURRENT LOAD CURRENT
(125mA) OPEN (250mA)
MAX1605 toc12
SUPPLY CURRENT (mA)
CURRENT LIMIT (mA)
SUPPLY CURRENT (µA)
OPEN
(500mA)
INPUT VOLTAGE
SUPPLY VOLTAGE
LOAD CURRENT (mA)
LINE TRANSIENT
MAX1605 toc13
LOAD TRANSIENT
MAX1605 toc14
SHUTDOWN WAVEFORM
MAX1605 toc15
IOUT 10mA/div 10mA 2V/div 18.1V 100mV/div 250mA/div 200µs/div VOUT 18V, ROUT 1.8k 3.3V, 3.6V VOUT 10V/div 500mA 250mA 500mA/div VSHDN 2V/div
18.1V 17.9V
17.9V 500mA
200µs/div 2.4V 5.5V VOUT 18V, ROUT 3.6k
40µs/div VOUT 18V, IOUT 10mA 3.3V, 3.6V
VOUT 100mV/div
Internal Switch Bias Supply SOT23 MAX1605
Description
NAME SHDN FUNCTION Active-Low Shutdown Input. logic shuts down device reduces supply current 0.1µA. Connect SHDN normal operation. Supply Voltage (+2.4V +5.5V). Bypass with 0.1µF greater capacitor. Ground Inductor Connection. drain internal N-channel MOSFET. high impedance shutdown. Inductor Current Limit Selection. Connect 500mA, leave floating 250mA, connect 125mA. Feedback Input. Connect resistive-divider network between output (VOUT) output voltage between 28V. feedback threshold 1.25V.
10µH
0.8V VOUT
2.4V 5.5V CONTROL LOGIC CURRENT LIMIT
VOUT
COUT
SHUTDOWN LOGIC
SHDN
ERROR AMPLIFIER 1.25V MAX1605
Figure Functional Diagram
Detailed Description
MAX1605 compact, step-up DC-DC converter operates from +2.4V +5.5V supply. Consuming only 18µA supply current, device includes internal switching MOSFET with on-resistance selectable current limit (Figure During startup, MAX1605 extends minimum off-time, limiting initial
surge current. MAX1605 also features shutdown mode.
Control Scheme
MAX1605 features minimum off-time, current-limited control scheme. duty cycle governed pair one-shots that minimum off-time maximum on-time. switching frequency
Internal Switch Bias Supply SOT23 MAX1605
(2.4V 5.5V) MAX1605 CONNECTION (2.4V 5.5V) MAX1605 (2.4V 5.5V) MAX1605
IPEAK 500mA
IPEAK 250mA
IPEAK 125mA
Figure Setting Peak Inductor Current Limit
500kHz depends upon load input voltage. peak current limit internal N-channel MOSFET selectable 125mA, 250mA, 500mA (Figure
below when MAX1605 shut down. capacitance load determine rate which decays. SHDN pulled high regardless input output voltages.
Setting Output Voltage (FB)
Adjust output voltage connecting voltagedivider from output (VOUT) (Figure Select between 200k. Calculate with following equation: [(VOUT VFB) where 1.25V VOUT range from 28V. input bias current maximum value 100nA, which allows large-value resistors used. less than error, current through should greater than times feedback input bias current (IFB).
Separate/Same Power
Separate voltage sources supply inductor (VIN) (VCC). This allows operation from low-voltage batteries well high-voltage sources (0.8V 28V) because chip bias provided logic supply (2.4V 5.5V) while output power sourced directly from battery Conversely, also supplied from supply remains within VCC's operating limits (+2.4V +5.5V).
0.8V VOUT 10µF 2.4V 5.5V 0.1µF SHDN
10µH
Current Limit Select (LIM)
MAX1605 allows selectable inductor current limit 125mA, 250mA, 500mA (Figure This allows flexibility designing higher current applications smaller, compact designs. lower current limit allows physically smaller inductor spacesensitive, low-power applications. Connect 500mA, leave floating 250mA, connect 125mA.
MAX1605 165k 2.2M
VOUT 10pF COUT
Shutdown (SHDN)
Pull SHDN enter shutdown. During shutdown, supply current drops 0.1µA enters highimpedance state. However, output remains connected input through inductor output rectifier, holding output voltage diode drop
Figure Typical Application Circuit
Internal Switch Bias Supply SOT23 MAX1605
Design Procedure
Inductor Selection
Smaller inductance values typically offer smaller physical size given series resistance saturation current. Circuits using larger inductance values start lower input voltages exhibit less ripple, also provide reduced output power. This occurs when inductance sufficiently large prevent maximum current limit from being reached before maximum on-time expires. inductor's saturation current rating should greater than peak switching current. However, generally acceptable bias inductor into saturation much 20%, although this will slightly reduce efficiency.
Input Bypass Capacitor
inputs, VIN, require bypass capacitors. Bypass with 0.1µF ceramic capacitor close possible. input supplies high currents inductor requires local bulk bypassing close inductor. 10µF low-ESR surface-mount capacitor sufficient most applications.
Board Layout Grounding
Careful printed circuit layout important minimizing ground bounce noise. Keep MAX1605's ground ground leads input output capacitors less than 0.2in (5mm) apart. addition, keep connections short possible. particular, when using external feedback resistors, locate them close possible. minimize output voltage ripple, maximize output power efficiency, ground plane solder directly ground plane. Refer MAX1605EVKIT evaluation layout example.
Picking Current Limit
peak current limit (ILX(MAX)) required application calculated from following equation:
ILX(MAX) VOUT VIN(MIN) OFF(MIN) VOUT IOUT(MAX) VIN(MIN)
Applications Information
Negative Voltage Bias
MAX1605 also generate negative output adding diode-capacitor charge-pump circuit (D1, shown Figure Feedback still connected positive output, which loaded, allowing very small capacitor value best stability lowest ripple, time constant R1-R2 series combination should near less than that effective load resistance. Output load regulation negative output somewhat looser than with standard positive output circuit, rise very light loads coupling through capacitance this objectionable, reduce resistance while maintaining their ratio, effectively preload output with hundred microamps. This R1-R2 values shown Figure about 10-times lower than typical values used positive-output design. When loaded, negative output voltage will slightly lower (closer ground approximately diode forward voltage) than inverse voltage
where tOFF(MIN) 0.8µs, VIN(MIN) minimum voltage used supply inductor. current limit must greater than this calculated value. Select appropriate current limit connecting VCC, GND, leaving unconnected (see Current Limit Select Figure
Diode Selection
high maximum switching frequency 500kHz requires high-speed rectifier. Schottky diodes, such Motorola MBRS0530 Nihon EP05Q03L, recommended. maintain high efficiency, average current rating Schottky diode should greater than peak switching current. Choose reverse breakdown voltage greater than output voltage.
Output Filter Capacitor
most applications, small ceramic surfacemount output capacitor, greater. small ceramic capacitors, output ripple voltage dominated capacitance value. tantalum electrolytic capacitors used, higher increases output ripple voltage. Decreasing reduces output ripple voltage peak-to-peak transient voltage. Surface-mount capacitors generally preferred because they lack inductance resistance their through-hole equivalents.
Output Disconnected Shutdown
When MAX1605 shut down, output remains connected input (Figure output voltage falls approximately 0.6V (the input voltage minus diode drop). applications that require output isolation during shutdown, external transistor shown Figure When MAX1605 active, voltage transistor's emitter exceeds input voltage, forcing transistor into
Internal Switch Bias Supply SOT23 MAX1605
0.8V VOUT 10µH 0.1µF VNEG -19V
D3** 0.1µF SHDN MAX1605 240k
2.4V 5.5V
1000pF
0.01µF
16.5k *D1, CENTRAL SEMICONDUCTOR CMPD7000 DUAL **D3 CENTRAL SEMICONDUCTOR CMSD4448 (1N4148)
Figure Negative Voltage Bias
saturation region. When shut down, input voltage exceeds emitter voltage inactive transistor provides high-impedance isolation between input output. Efficiency will slightly degraded transistor saturation voltage base current.
Chip Information
TRANSISTOR COUNT: 2329
0.8V VOUT
10µH
180k
2.4V 5.5V MAX1605 SHDN
VSET 18.3V (VOUT +0.3V) 2N2907A
VOUT
Figure Output Disconnected Shutdown
Internal Switch Bias Supply SOT23 MAX1605
Package Information
6LSOT.EPS
Internal Switch Bias Supply SOT23 MAX1605
NOTES
Internal Switch Bias Supply SOT23 MAX1605
NOTES
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 2000 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

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