Fujitsu MB3788 - Manuals

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Manual

Manual Fujitsu MB3788

Summary

Page 2 - • Output circuit; PIN ASSIGNMENT

MB3788 2 (Continued) • High-frequency operation: 100 kHz to 1 MHz• On-chip timer and latch-type short-circuit detection circuit• Wide error amplifier input voltage range: -0.2 V to V CC - 1.8 V • On-chip high-accuracy reference voltage circuit: 2.50 V ± 1% • Output circuit PNP transistor drive outpu...

Page 3 - PIN DESCRIPTION; Pin name

MB3788 3 ■ ■ ■ ■ PIN DESCRIPTION Note: The alphabetic characters in parenthesis above indicate the following input pins. (C): Comparator(E): Error amplifier Pin No. Pin name I/O Descriptions Channel 1 2 OUT1 O Channel 1 push-pull type output 3 VE1 I Channel 1 output current setting 4 Ca1 — Channel 1...

Page 4 - BLOCK DIAGRAM

MB3788 4 ■ ■ ■ ■ BLOCK DIAGRAM 24 Channel 1 -IN1 (E) FB1 -IN1 (C) +IN1 (E) 1 2 5 4 Ca1 V CC (out) OUT1 Cb1 11 13 14 3 CTL2 V CC CTL1 VE1 10 12 GND -IN(PWM) SCP V REF 1.9 V 1.3 V + - + - + - 1.5 V 0.6 V Error amplifier 1 Comparator 1 PWM comparator 1 OFF current setting 23 21 20 22 Channel 2 -IN2 (E)...

Page 5 - FUNCTIONAL DESCRIPTION; Major Functions; How to Set Output Current.; Channel Control Function; Voltage level at CTL pin

MB3788 5 ■ ■ ■ ■ FUNCTIONAL DESCRIPTION 1. Major Functions (1) Reference voltage power circuit The reference voltage power supply produces a reference voltage ( ≈ 2.50 V) which is temperature-compensated by the voltage supplied from the power pin (pin 11); it is used as the IC internal circuit opera...

Page 6 - Protection Functions; How to Set Time Constant for Timer & Latch-

MB3788 6 3. Protection Functions (1) Timer and latch-type short-circuit protection circuit The SCP comparator detects the output voltage levels of two comparators to detect an output short circuit. Ifthe output voltage of one comparator increases to 2.1 V, the transistor of the timer circuit is turn...

Page 8 - ELECTICAL CHARACTERISTICS

MB3788 8 ■ ■ ■ ■ ELECTICAL CHARACTERISTICS (Continued) (V CC =6V, T A = +25 ° C) Parameter Symbol Conditions Value Unit Min Typ Max Reference voltage Reference voltage V REF I OR = -1 mA 2.475 2.500 2.525 V Output voltage temperature variation ∆ V REF / V REF T A = -30 ° to +85 ° C -2 ± 0.2 2 % Inpu...

Page 10 - STANDARD CHARACTERISTIC CURVES

MB3788 10 ■ STANDARD CHARACTERISTIC CURVES (Continued) 2.5 2.0 1.5 1.0 0.5 0 0 4 8 12 16 20 Power current l CC (mA) Supply voltage V CC (V) 5 4 3 2 1 0 0 4 8 12 16 20 Reference voltage V REF ( V) Supply voltage V CC (V) CTL1, 2 = 6 V 5 4 3 2 1 0 0 1 2 3 4 5 Reference voltage V REF (V) Supply voltage...

Page 12 - HOW TO SET OUTPUT VOLTAGE; Note: Set the output voltage in the positive range (V

MB3788 12 ■ ■ ■ ■ HOW TO SET OUTPUT VOLTAGE + - V REF V OUT R NF R 1 R 2 R R V OUT = (R 1 + R 2 ) V REF 2 × R 2 Note: Set the output voltage in the positive range (V OUT > 0).

Page 13 - HOW TO SET OUTPUT CURRENT; • The OFF current time constant is proportional to the value of C; Fig.1 Output Circuit Diagram

MB3788 13 ■ ■ ■ ■ HOW TO SET OUTPUT CURRENT The output circuit is configured in a push-pull type as shown in Figure 1. The ON current value of the outputcurrent waveform shown in Figure 2 is a constant current and the OFF value set by RE is set by a time constant.Each output current can be calculate...

Page 15 - PROCESSING WITHOUT USING SCP PIN; Fig. 6 Processing without using SCP Pin

MB3788 15 ■ ■ ■ ■ PROCESSING WITHOUT USING SCP PIN If the timer and latch-type short-circuit protection circuit is not used, connect the SCP pin (pin 15) to GND asclose as possible. Also, connect the input pin of each channel comparator to the V CC pin (pin 11). Fig. 6 Processing without using SCP P...

Page 17 - φφφφ; Characteristic Measurement Diagram

MB3788 17 (Reference Data) The phase margin is halved by changing the smoothing capacitor from an aluminum electrolytic capacitor (Rc= 1.0 Ω ) to a semiconductor electrolytic capacitor (OS capacitor: Rc = 0.2 Ω ) with a low ESR (Figures 11 and 12). Fig. 10 DC/DC Converter A V - φφφφ Characteristic M...

Page 18 - APPLICATION CIRCUIT

MB3788 18 ■ ■ ■ ■ APPLICATION CIRCUIT +15 V +24 V DC motor 1 DC motor 2 24 150 Ω 23 20 21 22 1000 pF Channel 1 (dB) <Logic power supply> (b) 22 µ H 3 V 10 µ F Ca2 Cb2 OUT2 VE2 150 Ω 1000 pF <Logic power supply> + (a) 22 µ H 5 V 10 µ F Ca1 V CC (out) OUT1 VE1 2 3 5 1 4 Cb1 (15 mA) Channel...

Page 19 - NOTES ON USE; • Take measures against static electricity.; ORDERING INFORMATION; Part number

MB3788 19 ■ ■ ■ ■ NOTES ON USE • Take account of common impedance when designing the ear th line on a printed wiring board. • Take measures against static electricity. - For semiconductors, use antistatic or conductive containers.- When storing or carrying a printed circuit board after chip mounting...

Page 20 - PACKAGE DIMENSION; Each side

MB3788 20 ■ ■ ■ ■ PACKAGE DIMENSION 24-pin plastic SSOP (FPT-24P-M03) Note 1 ) *1 : Resin protrusion. ( Each side : + 0.15 ( .006 ) Max ) . Note 2 ) *2 : These dimensions do not include resin protrusion. Note 3 ) Pins width and pins thickness include plating thickness. Note 4 ) Pins width do not inc...

Page 21 - FUJITSU LIMITED; FUJITSU LIMITED Printed in Japan

MB3788 FUJITSU LIMITED All Rights Reserved. The contents of this document are subject to change without notice. Customers are advised to consult with FUJITSU salesrepresentatives before ordering.The information, such as descriptions of function and applicationcircuit examples, in this document are p...