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DS04-27209-3E

FUJITSU SEMICONDUCTOR

DATA SHEET

ASSP

SWITCHING REGULATOR
CONTROLLER

MB3788

DESCRIPTION 

The MB3788 is a dual-channel PWM-type switching regulator controller; it incorporates a reference voltage.
The MB3788 has a PWM circuit and an output circuit as well as a reference voltage power supply with a voltage
accuracy of 

±

1%.  The maximum operating frequency is 1 MHz.  It is designed for a voltage-drop output switching

regulator suitable for a logic power supply or speed control of a DC motor.
The MB3788 is compatible with all master ICs producing triangular waves, saw-tooth waves and sine waves with
an amplitude of 1.3 V to 1.9 V.
It can be used in high-performance portable equipment such as a video camcorder or notebook personal computer
(word processor).

FEATURES

• Wide operating power supply voltage range:  3.6 V to 18 V
• Low power dissipation
• Operating:  1.9 mA (standard)

Standby:  10 

µ

A Max

(Continued)

PACKAGE

This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields.  However, it is
advised that normal precautions be taken to avoid application of any voltage higher than maximum rated voltages to this high
impedance circuit.

24-pin Plastic SSOP

(FPT-24P-M03)

Summary of Contents for MB3788

Page 1: ...88 is compatible with all master ICs producing triangular waves saw tooth waves and sine waves with an amplitude of 1 3 V to 1 9 V It can be used in high performance portable equipment such as a video camcorder or notebook personal computer word processor FEATURES Wide operating power supply voltage range 3 6 V to 18 V Low power dissipation Operating 1 9 mA standard Standby 10 µA Max Continued PAC...

Page 2: ... circuit 2 50 V 1 Output circuit PNP transistor drive output pin Push pull type ON OFF current values set independently On chip standby function and output control function High density packaging SSOP 24P PIN ASSIGNMENT TOP VIEW VCC out OUT1 VE1 Cb1 Ca1 FB1 IN1 E IN1 E IN1 C IN PWN VCC VREF GND OUT2 VE2 Cb2 Ca2 FB2 IN2 E IN2 E IN2 C SCP CTL2 CTL1 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 ...

Page 3: ...n input 17 IN2 E I Channel 2 error amplifier non inversion input 18 IN2 E I Channel 2 error amplifier inversion input 19 FB2 O Channel 2 error amplifier output 20 Ca2 Channel 2 output transistor OFF current setting Output transistor OFF The current is set by connecting a capacitor between pins Ca2 and Cb2 21 Cb2 22 VE2 I Channel 2 output current setting 23 OUT2 O Channel 2 push pull type output Co...

Page 4: ...fier 1 Comparator 1 PWM comparator 1 OFF current setting 23 21 20 22 Channel 2 IN2 E FB2 IN2 C IN2 E Cb2 OUT2 Ca2 VE2 1 5 V 0 6 V Error amplifier 2 Comparator 2 PWM comparator 2 OFF current setting SCP comparator 2 1 V Low input voltage protection circuit SR latch circuit Reference voltage power 2 5 V Power channel ON OFF circuit Timer circuit 1 µA VREF 15 9 7 6 8 16 18 19 17 ...

Page 5: ...e error amplifier through a feedback resistor and capacitor allows setting of any loop gain to provide stable phase compensation 3 PWM comparator The PWM comparator controls the output pulse ON time according to the input voltage The voltage input to the IN pin PWM turns the output transistor on when it is lower than the output voltage of the error amplifier 4 Output circuit The output circuit is ...

Page 6: ...the capacitor voltage rises to the base emitter junction voltage VBE 0 65 V of the transistor See How to Set Time Constant for Timer Latch Type Short Circuit Protection Circuit When the protection circuit operates recycle the power to reset the circuit 2 Low input voltage malfunction fail safe circuit A transient at power on or an instantaneous supply voltage drop can cause a control IC malfunctio...

Page 7: ...ect reliability and could result in device failure No warranty is made with respect to uses operating conditions or combinations not represented on the data sheet Users considering application outside the listed conditions are advised to contact their FUJITSU representatives beforehand TA 25 C Parameter Symbol Conditions Ratings Unit Min Max Supply voltage VCC 20 V Control input voltage VICTL 20 V...

Page 8: ...parator Input offset voltage VIO 0 58 0 65 0 72 V Input bias current IIB VI 0 V 200 100 nA In phase input voltage range VICM 0 2 VCC 1 8 V Short circuit detector Threshold voltage VtPC 0 60 0 65 0 70 V Input standby voltage VSTB 50 100 mV Input latch voltage VI 50 100 mV Input source current IIbpc 1 4 1 0 0 6 µA Error amplifier Input offset voltage VIO VFB 1 6 V 10 10 mV Input offset current IIO V...

Page 9: ...rent IIM 120 µA Input source current IIM 2 mA Input bias current IIB VI 0 V 1 0 0 5 µA Control Threshold voltage Vth 0 7 1 4 2 1 V Input current IIH VCTL 5 V 100 200 µA IIL VCTL 0 V 10 10 µA Output Source current IO 40 mA Sink current IO RB 50 Ω 18 30 42 mA Output leak current ILO VO 18 V 20 µA All devices Standby current ICCO 0 10 µA Power current at output OFF ICC 1 9 2 7 mA ...

Page 10: ...ent setting pin voltage VE V VCC 6 V VCTL1 2 6 V IOR 1 mA 1 Power current supply voltage characteristic 2 Reference voltage supply voltage characteristic 3 Reference voltage output current setting pin voltage supply voltage characteristic 4 Reference voltage ambient temperature characteristic 3 0 2 8 2 6 2 4 2 2 2 0 0 1 2 3 4 5 Reference voltage VREF V Control voltage VCTL1 V 500 400 300 200 100 0...

Page 11: ...1000 800 600 400 200 0 20 020 406080 100 Power dissipation PD mW Ambient temperature TA C 7 Duty input oscillating frequency characteristic 8 Gain frequency characteristic and phase frequency characteristic f Hz 9 Power dissipation ambient temperature characteristic Circuit for measuring gain frequency characteristic and phase frequency characteristic 2 5 V out 2 5 V in 10 µF 240 kΩ 4 7 kΩ 4 7 kΩ ...

Page 12: ...MB3788 12 HOW TO SET OUTPUT VOLTAGE VREF VOUT RNF R1 R2 R R VOUT R1 R2 VREF 2 R2 Note Set the output voltage in the positive range VOUT 0 ...

Page 13: ... following expression ON current 1 5 RE A Output current setting pin voltage VE 1 5 V The OFF current time constant is proportional to the value of CB OFF current setting part RE CB Drive Tr OFF current ON current Output current 0 ON current OFF current t 22 µH 5 V 3 150 Ω 1000 pF 4 5 1 VCC Iout 1000 pF 10 µF IN1 E 8 2 kΩ IN1 C MB3788 2 Fig 1 Output Circuit Diagram Fig 2 Output Current Waveform Fi...

Page 14: ... SVP comparator outputs a Low level and transistor Q1 is turned off The short circuit protection capacitor CPE externally connected to the SCP pin starts to charge VPE 50 mV tPE 10 6 CPE 0 65 50 mV tPE 10 6 CPE CPE tPE 0 6 s Once the capacitor CPE is charged to about 0 65 V the SR latch is set and the output drive transistor is turned off At this time the duty cycle is made low and the output volt...

Page 15: ...atch type short circuit protection circuit is not used connect the SCP pin pin 15 to GND as close as possible Also connect the input pin of each channel comparator to the VCC pin pin 11 Fig 6 Processing without using SCP Pin 24 9 IN1 C VCC 16 IN2 C 15 GND SCP 11 ...

Page 16: ... smoothing capacitor with a low ESR reduces system stability Therefore attention should be paid to using semiconductor electrolytic capacitors such as OS capacitors or tantalum capacitors with a low ESP Phase margin reduction by using an OS capacitor is explained on the next page L Tr RC RL VIN D C 20 0 20 40 60 10 100 1k 10k 100k 0 90 180 10 100 1k 10k 100k 2 1 1 RC 0 Ω 2 RC 31 mΩ 2 1 Gain dB Fre...

Page 17: ... VIN Error amplifier VOUT CNF FB VIN R2 R1 VO IN IN VREF 2 62 AV ϕ 101001 k 10 k 100 k 60 40 20 0 20 40 180 90 0 90 180 VCC 10 V RL 25 Ω CP 0 1 µF Gain dB Frequency f Hz Aluminum electrolytic capacitor gain frequency and phase frequency characteristics DC DC converter 5 V output Aluminum electrolytic capacitor 220 µF 16 V Rc 1 0 Ω fOSC 1 kHz VO Phase deg GND AV ϕ 101001 k 10 k 100 k 60 40 20 0 20 ...

Page 18: ... VE1 2 3 5 1 4 Cb1 15 mA Channel 2 deg 10 µH 33 µF 33 µF VCC 11 6 9 7 8 IN1 E FB1 IN1 C IN1 E VCC 14 CTL2 13 CTL1 a 4 7 kΩ 4 7 kΩ 8 2 kΩ 2 7 kΩ 100 kΩ 19 16 18 17 IN2 E FB2 IN2 C IN2 E b 4 7 kΩ 4 7 kΩ 3 8 kΩ 2 7 kΩ 100 kΩ 15 10 12 GND IN PWM SCP VREF Triangular wave signal 1 9 V 1 3 V CT MB3785A used DC DC converter Analog power supply Sensor power supply DC motor speed control DC motor speed cont...

Page 19: ...board after chip mounting put it in a conductive bag or container The work table tools and measuring instruments must be grounded The worker must put on a grounding device containing 250 kΩ to 1 MΩ resistors in series Do not apply a negative voltage Applying a negative voltage of 0 3 V or less to an LSI may generate a parasitic transistor resulting in malfunction ORDERING INFORMATION Part number P...

Page 20: ...o not include tie bar cutting remainder Dimensions in mm inches Note The values in parentheses are reference values C 2003 FUJITSU LIMITED F24018S c 4 5 7 75 0 10 305 004 5 60 0 10 7 60 0 20 220 004 299 008 1 2 0 10 004 1 12 13 24 0 65 026 0 07 0 08 0 24 009 003 003 M 0 13 005 INDEX 0 17 0 03 007 001 A 0 25 010 0 10 0 10 004 004 Stand off Details of A part Mounting height 1 25 0 20 0 10 004 008 04...

Page 21: ...escribed in this document are designed developed and manufactured as contemplated for general use including without limitation ordinary industrial use general office use personal use and household use but are not designed developed and manufactured as contemplated 1 for use accompanying fatal risks or dangers that unless extremely high safety is secured could have a serious effect to the public an...

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