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FUJITSU SEMICONDUCTOR DATA SHEET DS04-27209-3E ASSP SWITCHING REGULATOR CONTROLLER MB3788 s 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). s 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) s 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 s PIN ASSIGNMENT (TOP VIEW) VCC(out) OUT1 VE1 Cb1 Ca1 FB1 -IN1(E) +IN1(E) -IN1(C) -IN(PWN) VCC VREF 1 2 3 4 5 6 7 8 9 10 11 12 (FPT-24P-M03) 24 23 22 21 20 19 18 17 16 15 14 13 GND OUT2 VE2 Cb2 Ca2 FB2 -IN2(E) +IN2(E) -IN2(C) SCP CTL2 CTL1 2 MB3788 s PIN DESCRIPTION Pin No. 2 3 4 Channel 1 5 6 7 8 9 16 17 18 Channel 2 19 20 21 22 23 13 Control circuit Pin name OUT1 VE1 Ca1 Cb1 FB1 -IN1(E) +IN1(E) -IN1(C) -IN2(C) +IN2(E) -IN2(E) FB2 Ca2 Cb2 VE2 OUT2 CTL1 I I I I O -- -- I O I I/O O I -- -- O I Descriptions Channel 1 push-pull type output Channel 1 output current setting Channel 1 output transistor OFF current setting: Output transistor OFF The current is set by connecting a capacitor between pins Ca1 and Cb1. Channel 1 error amplifier output Channel 1 error amplifier inversion input Channel 1 error amplifier non-inversion input Channel 1 comparator inversion input Channel 2 comparator inversion input Channel 2 error amplifier non-inversion input Channel 2 error amplifier inversion input Channel 2 error amplifier output Channel 2 output transistor OFF current setting: Output transistor OFF The current is set by connecting a capacitor between pins Ca2 and Cb2. Channel 2 output current setting Channel 2 push-pull type output Power and channel 1 control pin H level: Power and channel 1 operating L level: Standby Channel 2 control pin When CTL1 pin = H level, H level: Channel 2 operating L level: Channel 2 OFF Short-circuit protection circuit capacitor connection Output circuit power pin Master oscillating waveform input Reference power and control circuit power Reference voltage output Ground 14 15 1 10 CTL2 SCP VCC2 -IN(PWM) VCC1 VREF GND I -- -- I -- O -- Power circuit 11 12 24 Note: The alphabetic characters in parenthesis above indicate the following input pins. (C): Comparator (E): Error amplifier 3 MB3788 s BLOCK DIAGRAM Cb1 Channel 1 4 5 Ca1 +IN1 (E) -IN1 (E) FB1 8 + - Error amplifier 1 + PWM comparator 1 OFF current setting 1 VCC(out) 7 2 OUT1 6 + -IN1 (C) 9 Comparator 1 1.5 V 3 0.6 V - VE1 Ca2 Channel 2 20 21 Cb2 +IN2 (E) -IN2 (E) FB2 17 + - Error amplifier 2 + PWM comparator 2 OFF current setting 18 23 OUT2 19 + 0.6 V -IN2 (C) 16 Comparator 2 1.5 V 22 - VE2 Timer circuit 1 A SCP SCP comparator + 2.1 V 14 CTL2 1.9 V 1.3 V 15 VREF SR latch circuit Low input voltage protection circuit 10 11 VCC Reference Power/channel ON/OFF voltage circuit power (2.5 V) 13 CTL1 12 24 -IN(PWM) VREF GND 4 MB3788 s 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 L H CTL2 x H ON L *: The power current in the standby state is 10 A Max. OFF Power circuit Channel ON/OFF status Channel 1 Stand by state* ON Channel 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 s ABSOLUTE MAXIMUM RATINGS (TA = +25C) Parameter Supply voltage Control input voltage Allowable loss Operating ambient temperature Storage temperature Symbol VCC VICTL PD TOP Tstg Conditions -- -- Ratings Min -- -- -- Max 20 20 500* +85 +125 Unit V V mW C C Ta +25C -- -- -30 -55 *: 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. s RECOMMENDED OPERATING CONDITIONS (TA = +25C) Parameter Supply voltage Reference voltage output current Error amplifier input voltage Error amplifier input voltage Control input voltage Output current Operating frequency Operating ambient temperature Symbol VCC IOR VI VI VICTL IO fosc Top Conditions -- -- -- -- -- -- -- -- Values Min 3.6 -1 -0.2 -0.2 -0.2 3.0 100 -30 Typ 6.0 -- -- -- -- -- 300 25 Max 18 0 VCC - 1.8 VCC 18 30 1000 85 Unit V mA V V V mA kHz C 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 s ELECTICAL CHARACTERISTICS (VCC =6V, TA = +25C) Parameter Reference voltage Output voltage temperature variation Input stability Load stability Short-circuit output current Low voltage malfunction fail-safe circuit Threshold voltage Symbol VREF VREF/ VREF Line Load IOS VtH VtL Conditions IOR = -1 mA TA = -30 to +85C VCC = 3.6 V to 18 V IOR = -0.1 mA to 1 mA VREF = 2 V -- -- -- -- -- VI = 0 V -- -- -- -- -- VFB = 1.6 V VFB = 1.6 V VFB = 1.6 V -- -- AV = 0 dB -- -- -- VFB = 1.6 V VFB = 1.6 V Value Min 2.475 -2 -- -- -20 -- -- 80 1.5 0.58 -200 -0.2 0.60 -- -- -1.4 -10 -100 -200 -0.2 60 -- 60 VREF-0.3 -- -- -- Typ 2.500 0.2 2 3 -8 2.65 2.45 200 1.9 0.65 -100 -- 0.65 50 50 -1.0 -- -- -60 -- 100 800 80 2.4 0.05 120 -2 Max 2.525 2 10 10 -3 -- -- -- -- 0.72 -- VCC-1.8 0.70 100 100 -0.6 10 100 -- VCC-1.8 -- -- -- -- 0.5 -- -- Unit V % mV mV mA V V mV V V nA V V mV mV A mV nA nA V dB kHz dB V V A mA Reference voltage Hysteresis width Reset voltage VHYS VR VIO IIB VICM VtPC VSTB VI IIbpc VIO IIO IIB VICM AV BW CMRR VOM+ Short-circuit detection comparator Input offset voltage Input bias current In-phase input voltage range Threshold voltage Short-circuit detector Input standby voltage Input latch voltage Input source current Input offset voltage Input offset current Input bias current In-phase input voltage range Voltage gain Error amplifier Frequency bandwidth In-phase signal rejection ratio Maximum output voltage width VOMOutput sink current Output source current IOM+ IOM- (Continued) 8 MB3788 (Continued) Parameter Symbol Vt0 Threshold voltage Vt100 PWM comparator Input sink current Input source current Input bias current Threshold voltage Control Input current IIL Source current Output Sink current Output leak current Standby current All devices Power current at output OFF ICC -- -- 1.9 2.7 IO IO ILO ICCO VCTL = 0 V -- RB = 50 VO = 18 V -- -10 -- 18 -- -- -- -40 30 -- 0 10 -- 42 20 10 IIM+ IIMIIB Vth IIH VI = 0 V -- VCTL = 5 V Duty cycle = 100 % -- -- -- -- -- -1.0 0.7 -- 1.9 120 -2 -0.5 1.4 100 2.25 -- -- -- 2.1 200 V A mA A V A A mA mA A A mA Conditions Duty cycle = 0 % Values Min 1.05 Typ 1.3 Max -- Unit V 9 MB3788 s STANDARD CHARACTERISTIC CURVES 1. Power current - supply voltage characteristic 2.5 2.0 CTL1, 2 = 6 V Power 1.5 current lCC (mA) 1.0 0.5 0 0 4 8 12 16 20 Supply voltage VCC (V) 3.Reference voltage, output current setting pin voltage - supply voltage characteristic TA = +25C 5 4 3 Output 2 current setting pin voltage 1 VE (V) 0 1 2 3 4 5 Supply voltage VCC (V) 5. Reference voltage - control voltage characteristic VCC = 6 V TA = +25C 6. Control current - control voltage characteristic VCC = 6 V TA = +25C Reference 3 voltage VREF (V) 2 1 0 0 TA = +25C CTL1 = 6 V 2. Reference voltage - supply voltage characteristic 5 4 TA = +25C 4 8 12 16 20 Supply voltage VCC (V) 4. Reference voltage - ambient temperature characteristic 2.56 Reference 2.54 voltage VREF (V) 2.52 2.50 2.48 2.46 2.44 -60 -40 -20 0 20 40 60 80 100 Ambient temperature TA (C) VCC = 6 V VCTL1, 2 = 6 V IOR = -1 mA 5 4 Reference voltage 3 VREF (V) 2 1 0 0 VREF VE 3.0 2.8 Reference voltage 2.6 VREF (V) 2.4 2.2 2.0 0 500 400 Control current 300 lCTL1 (A) 200 100 0 1 2 3 4 5 0 4 8 12 16 20 Control voltage VCTL1 (V) Control voltage VCTL1 (V) (Continued) 10 MB3788 (Continued) 7. Duty - input oscillating frequency characteristic 100 Input waveform 80 60 40 20 -20 0 0 5K 10K 50K 100K 500K 1M -40 1K 10K 100K f (Hz) 9. Power dissipation - ambient temperature characteristic 1000 Circuit for measuring gain - frequency characteristic and phase - frequency characteristic 2.5 V 800 Power 600 dissipation PD (mW) 400 in 4.7 k 10 F -+ 4.7 k out + Error amplifier 200 4.7 k 4.7 k 2.5 V 240 k VCC = 6 V 1M 5M 10M -180 1.9V 1.3V VCC = 6 V VFB = 1.6 V TA = +25C 40 TA = +25C 180 90 Phase 0 (deg) -90 8.Gain - frequency characteristic and phase - frequency characteristic Duty Dtr (%) 20 Gain (dB) 0 Input oscillating frequency (Hz) 0 -20 020 4060 80 100 Ambient temperature TA (C) 11 MB3788 s HOW TO SET OUTPUT VOLTAGE VREF VOUT VOUT = R R1 VREF 2 x R2 (R1 + R2) + - R R2 RNF Note: Set the output voltage in the positive range (VOUT > 0). 12 MB3788 s 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 setting part OFF current Output 0 current OFF current ON current RE VE t Fig.1 Output Circuit Diagram Fig.2 Output Current Waveform 1000 pF 4 5 1 VCC 22 H Vout 10 F -IN1 (C) (5 V) 8.2 k 2.7 k Iout MB3788 2 1000 pF 3 150 -IN1 (E) Fig.3 Output Pin Voltage and Current Waveforms (Channel 1) Fig.4 Measurement Circuit Diagram 13 MB3788 s 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 S R Low PWM input voltage comparator protection circuit OUT Comparator 1 Comparator 2 + Q2 Q1 CPE SR latch-type circuit 2.1 V Fig. 5 Latch-Type Short-Circuit Protection Circuit 14 MB3788 s 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 s 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.) Tr L RC VIN D C RL Fig. 7 Basic Voltage-Drop Type DC/DC Converter Circuit 20 0 0 (2) Gain -20 (dB) -40 (1): RC = 0 (2): RC = 31 m (2) Phase -90 (deg) (1): RC = 0 (2): RC = 31 m -180 (1) (1) -60 10 100 1k Frequency f (Hz) 10k 100k 10 100 1k 10k 100k Frequency f (Hz) Fig.8 Gain - Frequency Characteristic Fig.9 Phase - Frequency Charecteristic 16 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 + VREF/2 Error amplifier -IN +IN AV - characteristic between VOUT and VIN R2 VIN R1 FB 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 -40 101001 k 10 k 100 k Frequency f (Hz) -90 -180 GND Aluminum electrolytic capacitor 220 F (16 V) Rc 1.0 : fOSC = 1 kHz Fig. 11 Gain - Frequency Characteristic OS capacitor gain - frequency and phase - frequency characteristics (DC/DC converter +5 V output) 60 AV 40 20 Gain (dB) 0 -20 -40 101001 k 10 k 100 k Frequency f (Hz) VCC = 10 V RL = 25 CP = 0.1 F 27 180 90 0 Phase (deg) + GND OS capacitor 22 F (16 V) Rc 1.2 : fOSC = 1 kHz VO+ -90 -180 Fig.12 Phase - Frequency Characteristic Curves 17 MB3788 s APPLICATION CIRCUIT 10 H VCC + + - 33 F 11 33 F 13 14 CTL1 CTL2 4.7 k 8 VCC +IN1 (E) Cb1 Ca1 4 4.7 k (a) 8.2 k 7 5 -IN1 (E) 2.7 k 0.22 F 100 k 6 Channel 1 (dB) VCC(out) OUT1 VE1 1 FB1 -IN1 (C) 2 9 3 4.7 k 17 18 20 (b) 1000 pF 22 H + 150 VE2 22 4.7 k (b) 3.8 k -IN2 (E) 100 k 19 3V 2.7 k 0.22 F Channel 2 (deg) Cb2 OUT2 21 23 FB2 -IN2 (C) 10 F 16 VREF 12 SCP 15 -IN(PWM) 10 GND 24 0.1 F Triangular wave signal 1.9 V 1.3 V CT +15 V +24 V DC motor 1 DC motor 2 18 MB3788 s 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. s ORDERING INFORMATION Part number MB3788PFV Package 24-pin Plastic SSOP (FPT-24P-M03) Remarks 19 MB3788 s PACKAGE DIMENSION 24-pin plastic SSOP (FPT-24P-M03) Note 1) Note 2) Note 3) Note 4) *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. *17.750.10(.305.004) 24 13 0.170.03 (.007.001) *2 5.600.10 INDEX 7.600.20 (.220.004) (.299.008) Details of "A" part 1.25 -0.10 .049 -.004 +0.20 +.008 (Mounting height) 0.25(.010) 0~8 1 12 "A" M 0.65(.026) 0.24 -0.07 .009 -.003 +0.08 +.003 0.13(.005) 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. Any information in this document, including descriptions of function and schematic diagrams, shall not be construed as license of the use or exercise of any intellectual property right, such as patent right or copyright, or any other right of Fujitsu or any third party or does Fujitsu warrant non-infringement of any third-party's intellectual property right or other right by using such information. Fujitsu assumes no liability for any infringement of the intellectual property rights or other rights of third parties which would result from the use of information contained herein. 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 (c) FUJITSU LIMITED Printed in Japan |
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