FUJITSU SEMICONDUCTOR DATA SHEET DS04-27209-3E 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 A Max (Continued) PACKAGE 24-pin Plastic SSOP (FPT-24P-M03) 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. MB3788 (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 VCC - 1.8 V * On-chip high-accuracy reference voltage 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) 1 24 GND OUT1 2 23 OUT2 VE1 3 22 VE2 Cb1 4 21 Cb2 Ca1 5 20 Ca2 FB1 6 19 FB2 -IN1(E) 7 18 -IN2(E) +IN1(E) 8 17 +IN2(E) -IN1(C) 9 16 -IN2(C) -IN(PWN) 10 15 SCP VCC 11 14 CTL2 VREF 12 13 CTL1 (FPT-24P-M03) 2 MB3788 PIN DESCRIPTION Pin No. Channel 1 Channel 2 Control circuit Power circuit Pin name I/O Descriptions 2 OUT1 O Channel 1 push-pull type output 3 VE1 I Channel 1 output current setting 4 Ca1 -- 5 Cb1 -- Channel 1 output transistor OFF current setting: Output transistor OFF The current is set by connecting a capacitor between pins Ca1 and Cb1. 6 FB1 O Channel 1 error amplifier output 7 -IN1(E) I Channel 1 error amplifier inversion input 8 +IN1(E) 9 -IN1(C) I Channel 1 comparator inversion input 16 -IN2(C) I Channel 2 comparator inversion 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 -- 21 Cb2 -- Channel 2 output transistor OFF current setting: Output transistor OFF The current is set by connecting a capacitor between pins Ca2 and Cb2. 22 VE2 I Channel 2 output current setting 23 OUT2 O Channel 2 push-pull type output 13 CTL1 I Power and channel 1 control pin H level: Power and channel 1 operating L level: Standby 14 CTL2 I Channel 2 control pin When CTL1 pin = H level, H level: Channel 2 operating L level: Channel 2 OFF 15 SCP -- Short-circuit protection circuit capacitor connection 1 VCC2 -- Output circuit power pin 10 -IN(PWM) I 11 VCC1 -- Reference power and control circuit power 12 VREF O Reference voltage output 24 GND -- Ground Channel 1 error amplifier non-inversion input Master oscillating waveform input Note: The alphabetic characters in parenthesis above indicate the following input pins. (C): Comparator (E): Error amplifier 3 MB3788 BLOCK DIAGRAM Cb1 Channel 1 4 5 Ca1 +IN1 (E) + 8 -IN1 (E) 7 FB1 6 OFF current setting + - Comparator 1 VCC(out) 2 OUT1 3 0.6 V - 9 1 PWM comparator 1 - + -IN1 (C) Error amplifier 1 VE1 1.5 V Ca2 Channel 2 20 21 Cb2 +IN2 (E) 17 -IN2 (E) 18 FB2 19 + OFF current setting + - PWM comparator 2 - + 0.6 V -IN2 (C) Error amplifier 2 16 Timer circuit 23 Comparator 2 OUT2 22 VE2 1.5 V - SCP comparator + 14 CTL2 11 VCC 13 CTL1 1.9 V 1.3 V 2.1 V 1 A SCP VREF 15 SR latch circuit 4 Low input voltage protection circuit Reference Power/channel ON/OFF voltage circuit power (2.5 V) 10 12 -IN(PWM) VREF 24 GND MB3788 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 operating power supply. The reference voltage can also be output externally at 1 mA from VREF pin (pin12). (2) Error amplifier The error amplifier detects the switching regulator output voltage and outputs a PWM control signal. It has a wide in-phase input voltage range of -0.2 V to VCC - 1.8 V to make setting from an external power supply easy. Connecting the output pin and inversion input pin of the 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 configured in a push-pull form and uses a PNP transistor drive system to drive a transistor of up to 30 mA. (See How to Set Output Current.) 2. Channel Control Function Channels can be set ON/OFF by combining the voltage levels at pin CTL1 (pin 13) and pin CTL2 (pin 14). Channel ON/OFF Setting Conditions Voltage level at CTL pin CTL1 CTL2 L x H H Channel ON/OFF status Power circuit Channel 1 Channel Stand by state* ON ON L OFF *: The power current in the standby state is 10 A Max. 5 MB3788 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. If the output voltage of one comparator increases to 2.1 V, the transistor of the timer circuit is turned off and the short circuit protection capacitor connected externally to the SCP pin (pin 15) starts charging. The latch circuit turns off the output transistor and simultaneously clears the duty cycle to 0 when the output voltage level of the comparator does not return to the normal voltage level until 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 & LatchType 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 malfunction, which may damage the system. The low input voltage malfunction fail-safe circuit detects the internal reference voltage level based on the supply voltage level, resets the latch circuit, turns off the output transistor, clears the duty cycle to 0 and holds the SCP pin (pin 15) at Low level. All circuits are recovered when the supply voltage is greater than the threshold voltage of the fail-safe circuit. 6 MB3788 ABSOLUTE MAXIMUM RATINGS (TA = +25C) Parameter Symbol Conditions Supply voltage VCC Control input voltage Ratings Unit Min Max -- -- 20 V VICTL -- -- 20 V Allowable loss PD Ta +25C -- 500* mW Operating ambient temperature TOP -- -30 +85 C Storage temperature Tstg -- -55 +125 C *: Value obtained when mounted on 4 cm x 4 cm double-sided epoxy substrate WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings. RECOMMENDED OPERATING CONDITIONS (TA = +25C) Parameter Symbol Conditions Supply voltage VCC Reference voltage output current Values Unit Min Typ Max -- 3.6 6.0 18 V IOR -- -1 -- 0 mA Error amplifier input voltage VI -- -0.2 -- VCC - 1.8 V Error amplifier input voltage VI -- -0.2 -- VCC V VICTL -- -0.2 -- 18 V IO -- 3.0 -- 30 mA Operating frequency fosc -- 100 300 1000 kHz Operating ambient temperature Top -- -30 25 85 C Control input voltage Output current WARNING: The recommended operating conditions are required in order to ensure the normal operation of the semiconductor device. All of the device's electrical characteristics are warranted when the device is operated within these ranges. Always use semiconductor devices within their recommended operating condition ranges. Operation outside these ranges may adversely affect 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. 7 MB3788 ELECTICAL CHARACTERISTICS (VCC =6V, TA = +25C) Parameter Reference voltage Low voltage malfunction fail-safe circuit Short-circuit detection comparator Short-circuit detector Error amplifier Symbol Conditions Value Unit Min Typ Max 2.475 2.500 2.525 V Reference voltage VREF IOR = -1 mA Output voltage temperature variation VREF/ VREF TA = -30 to +85C -2 0.2 2 % Input stability Line VCC = 3.6 V to 18 V -- 2 10 mV Load stability Load IOR = -0.1 mA to 1 mA -- 3 10 mV Short-circuit output current IOS VREF = 2 V -20 -8 -3 mA VtH -- -- 2.65 -- V VtL -- -- 2.45 -- V Hysteresis width VHYS -- 80 200 -- mV Reset voltage VR -- 1.5 1.9 -- V Input offset voltage VIO -- 0.58 0.65 0.72 V Input bias current IIB -200 -100 -- nA In-phase input voltage range VICM -- -0.2 -- VCC-1.8 V 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 A Input offset voltage VIO VFB = 1.6 V -10 -- 10 mV Input offset current IIO VFB = 1.6 V -100 -- 100 nA Input bias current IIB VFB = 1.6 V -200 -60 -- nA In-phase input voltage range VICM -- -0.2 -- VCC-1.8 V Voltage gain AV -- 60 100 -- dB Frequency bandwidth BW -- 800 -- kHz In-phase signal rejection ratio CMRR -- 60 80 -- dB VOM+ -- VREF-0.3 2.4 -- V VOM- -- -- 0.05 0.5 V Threshold voltage VI = 0 V AV = 0 dB Maximum output voltage width Output sink current IOM+ VFB = 1.6 V -- 120 -- A Output source current IOM- VFB = 1.6 V -- -2 -- mA (Continued) 8 MB3788 (Continued) Parameter Symbol Conditions Vt0 Duty cycle = 0 % Vt100 Duty cycle = 100 % Values Unit Min Typ Max 1.05 1.3 -- V -- 1.9 2.25 V Threshold voltage PWM comparator Input sink current IIM+ -- -- 120 -- A Input source current IIM- -- -- -2 -- mA Input bias current IIB -1.0 -0.5 -- A Threshold voltage Vth 0.7 1.4 2.1 V Control VI = 0 V -- IIH VCTL = 5 V -- 100 200 A IIL VCTL = 0 V -10 -- 10 A -- -40 -- mA Input current Output Source current IO -- Sink current IO RB = 50 18 30 42 mA Output leak current ILO VO = 18 V -- -- 20 A Standby current ICCO -- -- 0 10 A Power current at output OFF ICC -- -- 1.9 2.7 mA All devices 9 MB3788 STANDARD CHARACTERISTIC CURVES 1. Power current - supply voltage characteristic 2. Reference voltage - supply voltage characteristic TA = +25C CTL1 = 6 V 2.5 TA = +25C 5 2.0 4 CTL1, 2 = 6 V Power 1.5 current lCC (mA) 1.0 Reference 3 voltage VREF (V) 2 0.5 1 0 0 4 8 12 16 0 0 20 4 8 3.Reference voltage, output current setting pin voltage - supply voltage characteristic TA = +25C 5 4 Reference voltage 3 VREF (V) VE 2 3 4 VCC = 6 V VCTL1, 2 = 6 V IOR = -1 mA Reference 2.54 voltage VREF (V) 2.52 2.50 Output 2 current setting pin voltage 1 VE (V) 2.48 2.46 2.44 -60 -40 -20 0 20 40 60 80 100 Ambient temperature TA (C) 0 1 20 2.56 5 3 2 0 0 16 4. Reference voltage - ambient temperature characteristic 4 VREF 1 12 Supply voltage VCC (V) Supply voltage VCC (V) 5 Supply voltage VCC (V) 5. Reference voltage - control voltage characteristic VCC = 6 V TA = +25C 3.0 6. Control current - control voltage characteristic 2.8 400 Reference voltage 2.6 VREF (V) Control current 300 lCTL1 (A) 2.4 200 2.2 100 2.0 0 1 2 3 4 5 Control voltage VCTL1 (V) VCC = 6 V TA = +25C 500 0 0 4 8 12 16 20 Control voltage VCTL1 (V) (Continued) 10 MB3788 (Continued) 8.Gain - frequency characteristic and phase - frequency characteristic 7. Duty - input oscillating frequency characteristic 100 Input waveform Duty Dtr (%) VCC = 6 V VFB = 1.6 V TA = +25C 1.9V 1.3V 80 TA = +25C 40 90 20 Gain (dB) 0 60 40 180 Phase 0 (deg) 20 -90 -20 0 0 5K 10K 50K 100K 500K 1M Input oscillating frequency (Hz) -180 -40 1K 10K 100K 1M 5M 10M f (Hz) 9. Power dissipation - ambient temperature characteristic Circuit for measuring gain - frequency characteristic and phase - frequency characteristic 1000 2.5 V VCC = 6 V 2.5 V 240 k 800 4.7 k Power 600 dissipation PD (mW) 400 in 4.7 k 10 F - + out + Error amplifier 200 4.7 k 4.7 k 0 -20 020 4060 80 100 Ambient temperature TA (C) 11 MB3788 HOW TO SET OUTPUT VOLTAGE VREF VOUT VOUT = R R1 + - R R2 RNF Note: Set the output voltage in the positive range (VOUT > 0). 12 VREF 2 x R2 (R1 + R2) MB3788 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 output current 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 calculated from the 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. Drive Tr ON current CB OFF current OFF current setting part Output 0 current ON current RE OFF current VE t Fig.1 Output Circuit Diagram Fig.2 Output Current Waveform 1000 pF 4 -IN1 (C) VCC (5 V) 22 H 5 1 Iout MB3788 8.2 k 10 F 2.7 k 2 1000 pF 3 Fig.3 Output Pin Voltage and Current Waveforms (Channel 1) Vout -IN1 (E) 150 Fig.4 Measurement Circuit Diagram 13 MB3788 HOW TO SET TIME CONSTANT FOR TIMER & LATCH-TYPE SHORT-CIRCUIT PROTECTION CIRCUIT If the load conditions of the switching regulator are stable, the outputs of comparators 1 and 2 do not change, so the SP comparator outputs a High level. At this time, the SCP pin (pin 15) is held at about 50 mV. If the load conditions change suddenly due to a load short-circuit, for example, the output voltage of the comparator of the channel becomes a High-level signal (more than 2.1 V). Then, the 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 x 10-6/CPE 0.65 = 50 mV + tPE x 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 voltage of the SCP pin (pin 15) is held at Low level. This closes the SR latch input to discharge CPE. 2.5 V 1 A 15 Comparator 1 Comparator 2 + Q2 Q1 S CPE R SR latch-type circuit Low PWM input voltage comparator protection circuit 2.1 V Fig. 5 Latch-Type Short-Circuit Protection Circuit 14 OUT MB3788 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 as close as possible. Also, connect the input pin of each channel comparator to the VCC pin (pin 11). 11 VCC 9 -IN1 (C) 16 -IN2 (C) SCP 15 GND 24 Fig. 6 Processing without using SCP Pin 15 MB3788 EQUIVALENT SERIES RESISTANCE OF SMOOTHING CAPACITOR AND STABILITY OF DC/DC CONVERTER The equivalent series resistance (ESR) of the smoothing capacity in a DC/DC converter has a great effect on the loop phase characteristics. The ESR causes a small delay at the capacitor with a series resistance of 0 (Figures 8 and 9), thus improving system stability. On the other hand, using a 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 VIN D RL C Fig. 7 Basic Voltage-Drop Type DC/DC Converter Circuit 20 0 0 (2) Gain -20 (dB) (2) -40 (1): RC = 0 (2): RC = 31 m 100 (1) 1k 10k Frequency f (Hz) Fig.8 Gain - Frequency Characteristic 16 (1) (1): RC = 0 (2): RC = 31 m -180 -60 10 Phase -90 (deg) 100k 10 100 1k 10k 100k Frequency f (Hz) Fig.9 Phase - Frequency Charecteristic MB3788 (Reference Data) The phase margin is halved by changing the smoothing capacitor from an aluminum electrolytic capacitor (Rc = 1.0 ) to a semiconductor electrolytic capacitor (OS capacitor: Rc = 0.2 ) with a low ESR (Figures 11 and 12). VOUT VO+ CNF AV - characteristic between VOUT and VIN + - FB R2 -IN VIN +IN R1 VREF/2 Error amplifier Fig. 10 DC/DC Converter AV - Characteristic Measurement Diagram Aluminum electrolytic capacitor gain - frequency and phase - frequency characteristics (DC/DC converter +5 V output) 60 VCC = 10 V RL = 25 180 CP = 0.1 F 40 AV 90 VO+ 20 Gain + 62 (dB) Phase 0 (deg) 0 -20 -90 -40 101001 k 10 k 100 k -180 GND Aluminum electrolytic capacitor 220 F (16 V) Rc 1.0 : fOSC = 1 kHz Frequency f (Hz) Fig. 11 Gain - Frequency Characteristic OS capacitor gain - frequency and phase - frequency characteristics (DC/DC converter +5 V output) 60 VCC = 10 V RL = 25 CP = 0.1 F AV 40 20 Gain (dB) 0 180 90 27 0 VO+ Phase (deg) -20 -90 -40 101001 k 10 k 100 k -180 + GND OS capacitor 22 F (16 V) Rc 1.2 : fOSC = 1 kHz Frequency f (Hz) Fig.12 Phase - Frequency Characteristic Curves 17 MB3788 APPLICATION CIRCUIT 10 H VCC 13 + - + - 33 F 11 14 VCC CTL1 CTL2 4.7 k 8 Cb1 +IN1 (E) Ca1 5 VCC(out) 1 OUT1 2 8.2 k 7 2.7 k 0.22 F <Logic power supply> 4 1000 pF 4.7 k (a) Channel 1 (dB) -IN1 (E) 100 k 9 -IN1 (C) 17 +IN2 (E) VE1 5V + - 150 3 (15 mA) (b) 4.7 k Ca2 20 Cb2 21 OUT2 23 1000 pF 3.8 k 18 -IN2 (E) Channel 2 (deg) 100 k 19 FB2 16 -IN2 (C) VREF 12 22 H 3V + - 150 VE2 SCP -IN(PWM) GND 10 24 15 0.1 F 22 Triangular wave signal 1.9 V 1.3 V CT <Analog power supply> <Sensor power supply> +15 V +24 V <MB3785A-used DC/DC converter> <DC motor speed control> DC motor 1 <DC motor speed control> DC motor 2 18 10 F <Logic power supply> 4.7 k 2.7 k 0.22 F (a) 22 H FB1 6 (b) 33 F 10 F MB3788 NOTES ON USE * Take account of common impedance when designing the earth 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, 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 k to 1 M 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 MB3788PFV Package Remarks 24-pin Plastic SSOP (FPT-24P-M03) 19 MB3788 PACKAGE DIMENSION Note 1) Note 2) Note 3) Note 4) 24-pin plastic SSOP (FPT-24P-M03) *1 : Resin protrusion. (Each side : +0.15 (.006) Max) . *2 : These dimensions do not include resin protrusion. Pins width and pins thickness include plating thickness. Pins width do not include tie bar cutting remainder. 0.170.03 (.007.001) *17.750.10(.305.004) 24 13 *2 5.600.10 7.600.20 (.220.004) (.299.008) INDEX Details of "A" part +0.20 1.25 -0.10 +.008 .049 -.004 (Mounting height) 0.25(.010) 1 "A" 12 0~8 +0.08 0.65(.026) 0.24 -0.07 +.003 .009 -.003 0.13(.005) M 0.500.20 (.020.008) 0.600.15 (.024.006) 0.100.10 (.004.004) (Stand off) 0.10(.004) C 2003 FUJITSU LIMITED F24018S-c-4-5 Dimensions in mm (inches) . Note : The values in parentheses are reference values. 20 MB3788 FUJITSU LIMITED All Rights Reserved. The contents of this document are subject to change without notice. Customers are advised to consult with FUJITSU sales representatives before ordering. The information, such as descriptions of function and application circuit examples, in this document are presented solely for the purpose of reference to show examples of operations and uses of Fujitsu semiconductor device; Fujitsu does not warrant proper operation of the device with respect to use based on such information. When you develop equipment incorporating the device based on such information, you must assume any responsibility arising out of such use of the information. Fujitsu assumes no liability for any damages whatsoever arising out of the use of the information. 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The products described 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, and could lead directly to death, personal injury, severe physical damage or other loss (i.e., nuclear reaction control in nuclear facility, aircraft flight control, air traffic control, mass transport control, medical life support system, missile launch control in weapon system), or (2) for use requiring extremely high reliability (i.e., submersible repeater and artificial satellite). Please note that Fujitsu will not be liable against you and/or any third party for any claims or damages arising in connection with above-mentioned uses of the products. Any semiconductor devices have an inherent chance of failure. You must protect against injury, damage or loss from such failures by incorporating safety design measures into your facility and equipment such as redundancy, fire protection, and prevention of over-current levels and other abnormal operating conditions. If any products described in this document represent goods or technologies subject to certain restrictions on export under the Foreign Exchange and Foreign Trade Law of Japan, the prior authorization by Japanese government will be required for export of those products from Japan. F0309 FUJITSU LIMITED Printed in Japan