ASSP Power Supply Applications Pentium® DC/DC Converter MB38

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ASSP Power Supply Applications Pentium® DC/DC Converter MB38

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DS04-27218-4E
ASSP Power Supply Applications
Pentium® DC/DC Converter
MB3870
DESCRIPTION
FUJITSU MB3870 pulse width modulation (PWM) DC/DC converter chip that provides selection output voltages Pentium®* CPU's, using 5-bit input signal information. MB3870 utilizes synchronous rectification high efficiency features soft-start/discharge control function ease designing power supplies multi-supply systems, making ideal Pentium® power supply systems. Pentium registered trademark Intel Corporation.
FEATURES
Highly efficient using synchronous rectification scheme On-chip soft-start/discharge control circuit High precision output voltage: ±1.2% 5-bit, 32-step DAC: steps 2.05 steps Frequency range: using variable resistance (on-chip frequency setting capacitance) Standby current: On-chip PWRGOOD circuit output voltage state detection Timer-latch short-circuit protection circuit, overvoltage protection circuit output protection
PACKAGE
24-pin Plastic SSOP
(FPT-24P-M03)
MB3870
ASSIGNMENT
(Top view)
SGND OUT1 OUT2 PGND
VREF CSCP PWRGOOD VSENSE
(FPT-24P-M03)
MB3870
DESCRIPTION
Symbol SGND OUT1 Descriptions Triangular wave frequency setting resistor connection Discharging resistor connection soft start capacitor Ground Soft start capacitor connection (Also used discharge control) Error amplifier inverted input Error amplifier output Discharge control function enable/disable switch control Totem-pole output (External main-side gate drive) External main-side source-side connection Output bootstrap Insert capacitor between pins, bootstrap internal output transistor. Totem-pole output (External synchronous rectifier-side gate drive) Ground Output circuit power supply 5-bit digital input used DC/DC converter output voltage 5-bit digital input used DC/DC converter output voltage 5-bit digital input used DC/DC converter output voltage 5-bit digital input used DC/DC converter output voltage 5-bit digital input used DC/DC converter output voltage Power supply control level place standby mode. PWRGOOD circuit input PWRGOOD output (open-drain output) Outputs level signal when output voltage within range from VTLOW VTHIGH. Timer-latch short-circuit protection capacitor connection Power supply reference power control circuit Reference voltage output
OUT2 PGND VSENSE PWRGOOD
CSCP VREF
MB3870
BLOCK DIAGRAM
VSENSE POWERGOOD PWRGD
PWRGOOD (±10%)
Error Amp.
Overvoltage protection (17.5%) Comp.1 Comp.2
Drive
OUT1
Drive
OUT2 PGND
VSCP UVLO (5-bit) Comp. bias Power ON/OFF Comp. bias LOGIC
(3.5 CSCP VREF SGND
MB3870
OUTPUT VOLTAGE SETTING CODE
(DC/DC converter output voltage) 3.500 3.400 3.300 3.200 3.100 3.000 2.900 2.800 2.700 2.600 2.500 2.400 2.300 2.200 2.100 (output OFF) 2.050 2.000 1.950 1.900 1.850 1.800 1.750 1.700 1.650 1.600 1.550 1.500 1.450 1.400 1.350 1.300
MB3870
ABSOLUTE MAXIMUM RATINGS
Parameter Power supply voltage Bias voltage Boot voltage Control input voltage PWRGOOD output voltage Output current Peak output current Allowable dissipation Storage temperature Symbol VCTL VPWRGD Tstg +25°C Condition Duty 1/fOSC Duty) Value 740* +125 Unit
When mounted cm-square dual-sided epoxy base board WARNING: Semiconductor devices permanently damaged application stress (voltage, current, temperature, etc.) excess absolute maximum ratings. exceed these ratings.
MB3870
RECOMMENDED OPERATING CONDITIONS
Parameter Power supply voltage Bias voltage Boot voltage Reference voltage output current Symbol Input voltage Output current Peak output current Oscillator frequency Timing resistance Boot capacitance Reference voltage output capacitance Soft start capacitance Discharge control resistance Short detection capacitance Operating temperature fOSC CREF CSCP CTL, ENB, pins VSENSE PWRGOOD Duty 1/fOSC Duty) Condition Value Min. -100 -700 Typ. 4700 2200 Max. 10000 10000 Unit
WARNING: recommended operating conditions required order ensure normal operation semiconductor device. device's electrical characteristics warranted when device operated within these ranges. Always semiconductor devices within recommended operating conditions. Operation outside these ranges adversely affect reliability could result device failure. warranty made with respect uses, operating conditions, combinations represented data sheet. Users considering application outside listed conditions advised contact their FUJITSU representative beforehand.
MB3870
ELECTRICAL CHARACTERISTICS
+25°C, Parameter Output voltage Output voltage temperature regulation Input stability Load stability Short circuit output current Under voltage lockout circuit block (UVLO) Soft start block (CS) Threshold voltage Hysteresis voltage Reset voltage Charge current Symbol VREF VREF /VREF Line Load VRST Condition VREF -30°C +85°C* VREF CSCP 2200 Value Min. Typ. Max. 3.465 3.500 3.535 -2.8 0.63 -2.8 0.50 0.18 -2.0 0.68 -2.0 0.75 0.21 -1.2 0.73 -1.2 1.34 Unit
Reference voltage block (Ref)
Threshold voltage Short circuit Input source current ICSCP protection comparator block Short detection (SCP) tSCP interval Triangular wave oscillator block (OSC) Oscillator frequency fOSC Frequency temperature regulation f/fdt VTH1 Threshold voltage VTH2 temperature regulation Error amplifier block (Error Amp.) Input bias current Voltage gain Frequency bandwidth Output voltage Output source current Output sink current Standard design value VT/VT ISOURCE ISINK
-30°C +85°C* 00101 11010 -30°C +85°C*
1.7784
1.8000
1.8216
2.4700
2.5000
2.5300
-200 2.18
12.0
(Continued)
MB3870
+25°C, Parameter comparator blocks (PWM Threshold voltage Comp.1, Symbol Condition Value Min. Typ. 1.86 Max. Unit
Duty cycle Duty cycle OUT1 -100 OUT1 OUT2 -100 OUT2 IDIODE operating mode standby mode setting, VSENSE setting, VSENSE PWRGOOD PWRGOOD Discharge control Discharge control
Dead time control Maximum duty cycle block (DTC) Output voltage (main side) Output blocks (Drive1, Output voltage (synchronized rectifier side) Diode voltage Control block (CTL) input voltage Input current VDIODE ICTL VTLOW PWRGOOD comparator protection block (PWRGD) Threshold voltage VTHIGH Hysteresis voltage Output leak current Output voltage Discharge control comparator Threshold voltage Comp.) Discharge control input voltage ON/OFF block (CTL LOGIC) Input current ILEAK IENB
0.92 1.12 0.07
0.88 1.08 -1.0
0.90 1.10 0.06 0.05 -0.05
(Continued)
MB3870
(Continued)
Parameter Threshold voltage Over voltage protection comparator block Hysteresis voltage (OVP) VSENSE input current input voltage (VD4 input voltage pin) (D/A) Input current Standby current General Power supply current Symbol ISENSE ICCS Condition Min. 1.15 +25°C, Value Typ. Max. Unit
VSENSE
1.175 1.20 -0.1 0.05
VSENSE
MB3870
TYPICAL CHARACTERISTICS
Power supply current Power supply voltage characteristics
Power supply current (mA) 10.0 15.0 20.0 25.0 Power supply voltage +25°C
Reference voltage Power supply voltage characteristics
Reference voltage VREF 12.0 16.0 20.0 Power supply voltage
VREF Temperature characteristics
3.60 Reference voltage VREF 3.55
Reference voltage, current Control voltage
Reference voltage VREF ICTL 10.0 15.0 20.0 Control voltage VCTL 200.0 100.0 25.0 VREF +25°C 500.0 400.0 300.0 Control current ICTL (µA)
3.50
3.45 3.40 -40.0 -20.0
20.0
40.0
60.0
80.0 100.0
Temperature (°C)
threshold (3.5 setting) Temperature characteristics
threshold (3.5 setting) 3.55 threshold (2.0 setting) 3.60 2.04
threshold (2.0 setting) Temperature characteristics
2.02 2.00 1.98 1.94 -40.0 -20.0
3.50
3.45
3.40 -40.0 -20.0
20.0
40.0
60.0 80.0 100.0
20.0
40.0
60.0
80.0 100.0
Temperature (°C)
Temperature (°C)
(Continued)
MB3870
(Continued)
threshold (1.3 setting) Temperature characteristics
threshold (1.3 setting) 1.34 1.32 1.30 1.28 1.26 1.24 -40.0 -20.0
20.0
40.0
60.0
80.0 100.0
Temperature (°C)
Error Amp. gain, Phase Frequency characteristics Error Amp.
Gain (dB) +25°C Phase -135 -180 VREF
Frequency (HZ)
(Continued)
MB3870
(Continued)
Triangular wave oscillator frequency Power supply voltage characteristics
Oscillator frequency fosc (kHz) Oscillator Frequency fosc (kHz)
Triangular wave oscillator frequency Timing resistance characteristics
1000
10.0 12.0 14.0 16.0 18.0 20.0 Power supply voltage
Timing resistance 1000
Triangular wave oscillator frequency Temperature characteristics
Oscillator frequency fosc (kHz)
-40.0 -20.0
20.0
40.0
60.0
80.0 100.0
Temperature (°C)
MB3870
FUNCTION DESCRIPTION
Switching Regulator Function
Reference voltage circuit (Ref) reference voltage circuit uses voltage supply from (pin generate temperature compensated reference voltage reference voltage internal circuits chip. also possible supply reference voltage output external circuits through VREF (pin 24). Triangular wave oscillator (OSC) triangular wave form generated using on-chip frequency selection capacitor, plus frequency selection resistance connected (pin triangular wave input comparator circuits Error amplifier (Error Amp.) error amplifier circuit used detect output voltage from DC/DC converter output control signal. in-phase input range covers full range from connecting feedback resistance capacitor between (pin (pin possible create desired level loop gain, thereby providing stable phase compensation system. Also, possible prevent current spikes power supply start-up connecting soft start capacitor (pin non-inverting input Error Amp. Error Amp. soft start detection makes possible system operate fixed soft start time that independent output load converter. comparators (PWM Comp.1, Comp.2) Comp.1 Comp.2 voltage-pulse width converters that control output voltage according input voltage. Comp.1 controls pulse width main-side output circuit, Comp.2 controls pulse width synchronous rectifier side output circuit. triangular wave generated triangular wave oscillator compared with output voltage from Error Amp., during intervals when Error Amp. output higher than triangular wave, main-side output transistor switched synchronous rectifier side output transistor turned off. Comp.1 maximum duty cycle approximately 90%. Output circuits (Drive1, Drive2) output circuits both main-side synchronous rectifier-side have totem-pole configuration, capable driving external N-ch. FET. Power supply control circuit (CTL) This circuit able control power supply ON/OFF switching from (pin 19). (During standby mode, supply current TYP.) circuit (D/A) This circuit controls output voltage between selected 5-bit (32-step) input signal information. output voltage steps between steps between 2.05 When input pins through (pin through level, DC/DC converter output voltage
MB3870
Protection Functions
under voltage lockout circuit (UVLO) Power surges power-on, momentary under-voltage situations cause abnormal operation MB3870, which lead damage deterioration systems. This circuit prevents abnormal operation during times voltage using supply voltage detect level internal reference voltage, fixes output pins OUT1 (pin OUT2 (pin level. Once supply voltage recovers level above threshold voltage under voltage lockout circuit, operation restored. Timer-latch short-circuit protection circuit (SCP) This circuit detects output voltage level from Error Amp. activates timer circuit, charging external capacitor from CSCP (pin when Error Amp. output voltage level reaches exceeds about Error Amp. output does return normal voltage range before capacitor voltage reaches about 0.68 latch circuit activated output pins (OUT1, OUT2) held level. Once protector circuit activated, reset switching power supply again. Overvoltage protection circuit (OVP) When DC/DC converter output voltage (VO) exceeds output voltage pins more than +17.5%, overvoltage protection circuit output signal goes level causing output (OUT1) held level other output (OUT2) held level. PWRGOOD comparator detection circuit (PWRGD) PWRGOOD (pin outputs level signal long VSENSE (pin receiving DC/DC converter output voltage (VO) within range times output voltage pins.
Soft Start/Discharge Control
Soft start circuit (CS) Connecting capacitor (pin prevents inrush current power turnon. Using Error Amp. detecting soft error allows soft start time initiated independent output load from DC/DC converter. Discharge control ON/OFF circuit (CTL LOGIC) Entering level signal while level signal input causes discharge control ON/OFF circuit (CTL LOGIC) switch soft start circuit (CS) from charging discharging. resistance (RS) connected (pin charges soft start capacitor (CS), that Error Amp. provides control over DC/DC converter output voltage same during soft start. This makes possible control voltage drop independently output load. When voltage reaches discharge control comparator circuit Comp.) threshold voltage mV), discharge control canceled. When level signal input (pin DC/DC converter output voltage discharge time control switched OFF.
MB3870
METHOD SETTING SOFT START TIME
startup MB3870, capacitor (CS) connected begins charging. This produces soft start, providing output voltage from Error Amp. that proportional voltage regardless DC/DC converter load current. Soft start time (time output setting voltage (sec) (µF) (µA)
TIME SETTING SHORT DETECTION
When load conditions change rapidly with reduced output voltage, when load fault occurs, Capacitor Cscp connected CSCP (pin charged threshold voltage (VTH:=0.68V) sets latch, external turned (inactive interval 100%). Short detection time (sec) 0.68 CSCP (µF) (µA)
OSCILLATOR FREQUENCY SETTING
oscillator frequency connecting resistance (pin Oscillator frequency fOSC (kHz) 26250
METHOD SETTING DISCHARGE TIME
level signal while level causes resistance (RS) connected discharge electrical charge capacitor (CS) connected pin, causing output voltage fall gradually regardless DC/DC converter load current. Discharge time (time 0.05 output voltage) toff (msec) (µF) COMP)
long level, discharge control function switched OFF.
BLOCK SWITCHING
Switching signal during MB3870 operation cause transient fluctuation output voltage from DC/DC converter. resulting voltage instability cause level from PWRGOOD block, activating protection shutting output from DC/DC converter. switch settings, first input level control signal place MB3870 standby status. When signals level, DC/DC converter output switched OFF.
MB3870
PWRGOOD COMPARATOR CIRCUIT, CIRCUIT OPERATION TIMING CHART
signal DC/DC output voltage
1.175
PWRGOOD signal OUT1 signal OUT2 signal
Operation when signal "High".
1.175
Hysteresis voltage Hysteresis voltage Hysteresis voltage
DC/DC output voltage
PWRGOOD OUT2
MB3870
LOGIC CIRCUIT OPERATION TIMING CHART
signal signal VREF output voltage voltage DC/DC output voltage
0.05 toff
DC/DC CONVERTER INPUT VOLTAGE (Vin) VOLTAGE SETTING
voltage bootstrapped from voltage amount equivalent voltage, result bootstrap capacitance (CB) between pin. Therefore, either voltage voltage should adjusted that DC/DC converter block input voltage plus voltage does exceed recommended operating conditions boot voltage (VCB).
DC/DC converter block
Drive
OUT1
Drive
OUT2 PGND
connect external diode (Schottky barrier diode) makes voltage drop reduced then perform higher efficiency. switching noise reduced connecting resistance when external MOSFET gate input capacitance (Ciss) large, caused external MOSFET gate drive current limiting resistance.
MB3870
DC/DC CONVERTER SWITCHING OPERATION WAVEFORMS
00001 (2.0 load: fosc setting
<VCC OUT1 OUT2 OUT1 OUT2
(µs)
expansion
OUT1 OUT2
-0.5 -1.5 OUT1 OUT2 OUT2 OUT1
(µs)
(µs)
Synchronous rectifier length: (typ) OUT1 (typ) OUT2 (typ)
Synchronous rectifier length: (typ) OUT1 (typ) OUT2 (typ)
Output voltage setting signals
MB3870
PWRGOOD POWERGOOD PWRGD (±10%) (17.5%) Comp1 OUT1 0.33 2SK2983 0.33 Drive Comp2 OUT2 PGND Comp bias LOGIC pin) RB415D 2SK2983 Over voltage protection
VSENSE
APPLICATION EXAMPLE
Error
12000 Drive
4700
MBRS130LT3
Comp VSCP
bit) bias UVLO PowerON/OFF (3.5 CSCP 2200 VREF SGND 0.33 0.33
Note:
2SK2983:NEC Corporation RB415d:ROHM Co.,ltd. MBRS130LT3:Motorola Inc.
MB3870
REFERENCE DATA
Conversion efficiency Load current characteristics (Output voltage
Conversion efficiency
Load current
10.0
100.0
(Continued)
MB3870
(Continued)
Transient response ON/OFF (Output nonload)
CTL(V) 4700
(ms)
(mV) IO(A)
Transient response load abrupt change (Output
100µs
1000 (µs)
MB3870
USAGE PRECAUTIONS
Device settings must exceed absolute maximum ratings.
Usage under conditions exceeding absolute maximum ratings permanently damage devices. Note also that normal operation usage within recommended operating conditions preferred, that reliability devices adversely affected when used outside these conditions.
Devices should used within recommended operating conditions.
Recommended operating conditions recommended values within which device warranted operate normally. Rated values electrical characteristics warranted within range recommended operating conditions within conditions listed condition column each parameter.
Printed circuit board ground lines should designed consideration common impedance values. Observe precautions against static electricity.
Containers which semiconductors placed should either protected against static electricity, conductive material. After mounting devices, conductive bags conductive containers when storing transporting printed circuit boards. Working surfaces, tools instruments should properly grounded. Workers should grounded ground line with resistance series between worker ground.
ORDERING INFORMATION
Part number MB3870 PFV-G-BND Package 24-pin Plastic SSOP (FPT-24P-M03) Remarks
MB3870
PACKAGE DIMENSION
24-pin Plastic SSOP (FPT-24P-M03)
These dimensions include resin protrusion.
7.75±0.10(.305±.004)
1.25 -0.10 .049 -.004
+0.20 +.008
(Mounting height)
0.10(.004)
5.60±0.10
INDEX (.220±.004)
7.60±0.20 (.299±.008)
6.60(.260)
0.65±0.12(.0256±.0047)
0.22 -0.05 .009
+0.10 +.004 -.002
0.15 -0.02 .006 -.001
+0.05 +.002
Details part 0.10±0.10(.004±.004) (STAND OFF)
7.15(.281)REF
0.50±0.20 (.020±.008)
1994 FUJITSU LIMITED F24018S-2C-2
Dimensions (inches)
MB3870
FUJITSU LIMITED
further information please contact:
Japan FUJITSU LIMITED Corporate Global Business Support Division Electronic Devices KAWASAKI PLANT, 4-1-1, Kamikodanaka Nakahara-ku, Kawasaki-shi Kanagawa 211-8588, Japan Tel: 81(44) 754-3763 Fax: 81(44) 754-3329
Rights Reserved. contents this document subject change without notice. Customers advised consult with FUJITSU sales representatives before ordering. information circuit diagrams this document presented examples semiconductor device applications, intended incorporated devices actual use. Also, FUJITSU unable assume responsibility infringement patent rights other rights third parties arising from this information circuit diagrams. FUJITSU semiconductor devices intended standard applications (computers, office automation other office equipment, industrial, communications, measurement equipment, personal household devices, etc.). CAUTION: Customers considering products special applications where failure abnormal operation directly affect human lives cause physical injury property damage, where extremely high levels reliability demanded (such aerospace systems, atomic energy controls, floor repeaters, vehicle operating controls, medical devices life support, etc.) requested consult with FUJITSU sales representatives before such use. company will responsible damages arising from such without prior approval. semiconductor devices have inherent chance failure. must protect against injury, damage loss from such failures incorporating safety design measures into your facility equipment such redundancy, fire protection, prevention over-current levels other abnormal operating conditions. products described this document represent goods technologies subject certain restrictions export under Foreign Exchange Foreign Trade Japan, prior authorization Japanese government will required export those products from Japan.
http://www.fujitsu.co.jp/
North South America FUJITSU MICROELECTRONICS, INC. Semiconductor Division 3545 North First Street Jose, 95134-1804, Tel: (408) 922-9000 Fax: (408) 922-9179 Customer Response Center Mon. Fri.: (PST) Tel: (800) 866-8608 Fax: (408) 922-9179
http://www.fujitsumicro.com/
Europe FUJITSU MIKROELEKTRONIK GmbH Siebenstein 6-10 D-63303 Dreieich-Buchschlag Germany Tel: (06103) 690-0 Fax: (06103) 690-122
http://www.fujitsu-ede.com/
Asia Pacific FUJITSU MICROELECTRONICS ASIA #05-08, Lorong Chuan Tech Park Singapore 556741 Tel: (65) 281-0770 Fax: (65) 281-0220
http://www.fmap.com.sg/
F9903 FUJITSU LIMITED Printed Japan

ASSP Power Supply Applications Pentium® DC/DC Converter MB38

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