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FUJITSU SEMICONDUCTOR DATA SHEET
DS04-27205-4E
ASSP Power Supplies
BIPOLAR
Switching Regulator Controller
MB3782
s DESCRIPTION
The FUJITSU MB3782 is a PWM-type switching regulator controller, designed with open-collector output for connection to external drive transistors and coils, providing a selection of three types of output voltage: stepup, step-down or inverting (inverting output is available on one circuit only). The MB3782 features identical oscillator output waveforms to enable completely synchronous operation and prevent the occurrence of low-frequency beat between channels. Also, the MB3782 features low power dissipation (2.1 mA typ) and a built-in standby mode (10 A), making possible the configuration of a wide variety of high-efficiency, stable power supplies, even with the use of battery power. The MB3782 is an ideal power supply for high-performance portable devices such as video camcorders and cameras.
s FEATURES
* * * * * * * * Wide voltage range (3.6 to 18 V) Low power dissipation (operating mode: 2.1 mA (typ), standby mode: 10 A (max) Wide range of oscillator frequencies, high-frequency capability (1 to 500 kHz) On-chip timer-latch type short detection circuit On-chip undervoltage lockout circuit On-chip 2.50 V reference voltage circuit (1.25 V output available at RT pin) Dead time adjustment over full duty cycle range On-chip standby mode (power on/off function)
(Continued)
s PACKAGE
Plastic DIP 20 pin , Plastic SOP 20 pin ,
(DIP-20P-M01)
(FPT-20P-M01)
MB3782
s PIN ASSIGNMENT
TOP VIEW
VREF CT RT + IN1 - IN1 FB1 DTC1 PUT1 GND OUT2 1 2 3 4 5 6 7 8 9 10 VCC CTL - IN3 FB3 DTC3 OUT3 SCP - IN2 FB2 DTC2
20 19 18 17 16 15 14 13 12 11
(DIP-20P-M01) (FPT-20P-M01)
s PIN DESCRIPTION
Pin No. 1 2 Pin Name VREF CT I/O O -- Description 2.50 V (typ) voltage output: provides load current up to 3 mA, for use as error amplifier reference input and for dead time setting. Oscillator timing capacity connection: should be used in the capacity range 150 to 15000 pF. Oscillator timing resistor connection: should be used in the resistance range 5.1 to 100 k. This pin can also provide output at voltage level VREF/2, for use as error amplifier reference input. Error amplifier 1 non-inverting input pin. Error amplifier 1 inverting input pin. Error amplifier 1 output pin: connect resistor and capacitor between this pin and the -IN1 pin to set gain and adjust frequency characteristics. OUT1 dead time setting pin: VREF voltage is divided by an external resistor and applied to set dead time. Also, a capacitor may be connected between this pin and the GND pin to perform soft start operations.
3 4 5 6
RT +IN1 -IN1 FB1
-- I I O
7
DTC1*
1
I
(Continued)
2
MB3782
(Continued) Pin No.
8 9 10
Pin Name VOUT1 GND OUT2
I/O O -- O
Description Open collector type output pin with an emitter connected to GND. Output current may be up to 50 mA. Ground pin Open collector type output pin with an emitter connected to GND. Output current may be up to 50 mA. Used to set OUT2 pin dead time. VREF voltage is divided by an external resistor and applied to set dead time. Also, a capacitor may be connected between this pin and the GND pin to perform soft start operations. Error amplifier 2 output pin: connect resistor and capacitor between this pin and the -IN2 pin to set gain and adjust frequency characteristics. Error amplifier 2 inverting input pin. Time constant setting capacitor connection for timer-latch type short prevention circuit: a capacitor should be connected between this pin and the GND pin. For details, see "s Setting the Time Constant for the Timer-Latch Type Short Prevention Circuit." Open collector type output pin for emitter connected to GND. Output current may be up to 50 mA. Used to set OUT3 pin dead time. VREF voltage is divided by an external resistor and applied to set dead time. Also, a capacitor may be connected between this pin and the GND pin to perform soft start operations. Error amplifier 3 output pin: connect resistor and capacitor between this pin and the -IN3 pin to set gain and adjust frequency characteristics. Error amplifier 3 inverting input pin. Power supply control pin: low level places the IC in standby mode and reduces power consumption to 10 A or lower. Input level may be driven by TTL or CMOS. Power supply pin: voltage range is 3.6 to 18 V.
11
DTC2*1
I
12 13
FB2 -IN2
O I
14
SCP*2
--
15
OUT3
O
16
DTC3*
1
I
17 18 19 20
FB3 -IN3 CTL VCC
O I I --
(Continued)
*1: DTC = Dead Time Control *2: SCP = Short Circuit Protection
3
MB3782
s BLOCK DIAGRAM
RT
3
CT
2
VREF
1
VCC
20
CLT
19
1.25 V
2.5 V
Triangular wave oscillator
Reference voltage source
Power on/off control circuit
9
GND
Error Amp.1 + IN1 - IN1 FB1 DTC1
4
PWM Comp. Ch.1 + + -
8
+ -
OUT1
5
6 7
Error Amp.2 - IN2
13
PWM Comp. + + -
- + 1.25 V
Ch.2
10
OUT2
FB2 DTC2
12 11
Error Amp.3 - IN3
18
PWM Comp. + + -
- + 1.25 V
Ch.3
15
OUT3
FB3 DTC3
17
16
SCP Comp. - - - + 2.1 V VREF 1 A SCP
14
S Latch
R U.V.L.O.
4
MB3782
s FUNCTIONAL DESCRIPTIONS
1. Reference Voltage Source
The reference voltage source uses the voltage provided at the power supply pin (pin 20) to generate a temperature-compensated reference voltage ( 2.50 V), which is used as the operating power supply for the internal circuits of the IC. The reference voltage source can be output through the VREF pin (pin 1).
2. Triangular Wave Oscillator
By connecting a timing capacitor and resistor respectively to the CT pin (pin 2) and RT pin (pin 3), the oscillator can provide a triangular waveform at any desired frequency. The waveform has an amplitude of 1.3 V to 1.9 V, and can be connected to the non-inverting input of the onchip PWM comparator and also output through the CT pin.
3. Error Amps
The error amps are amplifiers that detect the output voltage of the switching regulator and send the PWM control signal. The common-mode input voltage range is 1.05 V to 1.45 V, so that the voltage applied to the non-inverting input pin as a reference voltage should be either the voltage obtained by dividing the IC reference voltage output (recommended value: VREF/2) or the voltage obtained from the RT pin (1.25 V). The non-inverting input for the error amps 1 and 2 is internally connected to VREF/2 voltage. Also, a feedback transistor and capacitor can be connected between the error amp output pin and inverting input pin to provide any desired level of loop gain, enabling stable phase compensation.
4. Timer Latch (S-R Latch) Type Short Prevention Circuit
The timer-latch type short prevention circuit detects the output levels from each of the error amps. Whenever one or more error amps produces an output level of 2.1 V or higher, the timer circuit is activated starting the charging of the external protection enabler capacitor. If the error amp output voltage does not return to normal range before the voltage in this capacitor reaches the transistor's base-emitter junction voltage (VBE ( 0.65 V)), the latch circuit will operate to turn the output transistor off and at the same time set the dead time to 100%. Once the prevention circuit is activated, the power must be switched on again to resume normal operation.
5. Low Input Voltage Fault Prevention Circuit (Under Voltage Lock-Out (UVLO) function)
When power is switched on, excess power or momentary drops in power line current can cause operating faults in the controller IC, which can in turn lead to damage or deterioration in systems. The low input voltage fault prevention circuit detects the internal reference voltage level with respect to the power supply voltage level and acts to reset the latch circuit, thereby turning the output transistor off and at the same time setting the dead time to 100% and holding the SCP pin (pin 14) at "low." Operation returns to normal when the power supply voltage reaches or exceeds the UVLO threshold voltage level.
6. PWM Comparator
The PWM comparator is a voltage comparator with one inverting and two non-inverting inputs, which acts as a voltage to pulse width converter controlling the on-time of the output pulse according to the input voltage level. When the triangular waveform produced by the oscillator is lower than either the error amp output or the DTC pin voltage, the output transistor is switched on. 5
MB3782
It is also possible to use the DTC terminal to provide a soft start function.
7. Output Transistor
The output is open-collector type, with the emitter of the output transistor connected to the GND pin. The power transistor for external switching can carry a base current of up to 50 mA.
8. Power Supply Control
Power supply on/off control is enabled through the CTL pin (pin 19). (In standby mode, power supply current is 10 A or less.)
6
MB3782
s SETTING THE TIME CONSTANT FOR THE TIMER-LATCH TYPE SHORT PREVENTION CIRCUIT
Figure 1 shows the configuration of the protection latch circuit. The output lines from the error amps are each connected to the inverting input lines of the short protection comparator, which constantly compares them with the reference voltage of approximately 2.1 V connected to the non-inverting input. When load conditions in the switching regulator are stabilized, there is no variation in the output from the error amps, and therefore the short prevention controls are held in equilibrium. In this situation, voltage at the SCP pin (pin 14) is held at approximately 50 mV. When load conditions change rapidly, as in the case of a load short, high potential signal (greater than 2.1V) from the error amps is input to the inverting signal input of the short protection comparator, and the short protection comparator outputs a "low" level signal. The transistor Q1 is consequently switched off, so that short protection capacitor CPE externally connected to the SCP pin voltage is then charged according to the following formulas. VPE = 50 mV + tPE x 10-6/CPE 0.65 = 50 mV + tPE x 10-6/CPE CPE = tPE/0.6 (F) When the short protection capacitor is charged to a level of approximately 0.65 V, the SR latch is set and the low input voltage fault prevention circuit is enabled, turning the output drive transistor off. At the same time, the dead time is set to 100% and the SCP pin (pin 14) is held "low." This closes the S-R latch input and then discharges the capacitor CPE
2.50 V 1 A S.C.P.Comp. Error Amp.1 Error Amp.2 Error Amp.3 2.1 V - - - + 14 CPE Q1 Q3 S R U.V.L.O. PWM Comp. Out
Latch
Figure 1
Protection Latch Circuit
7
MB3782
s SETTING OUTPUT VOLTAGE
The following diagrams show the connections used to set the output voltage. Because the power supply to the error amps is provided by the same reference voltage circuit used for the other internal circuits, the common-mode input voltage range is set at 1.05 V to 1.45 V. The reference voltage input to the +IN and -IN pins should be set at 1.25 V (VREF/2). The method of connection for channel 1 is different from channel 2 and channel 3. In addition, channel 1 is capable of picking up both positive and negative voltages, while channel 2 and channel 3 can pick up only positive output voltages.
VREF V0 + R R1 V0 + = VREF * (R1 + R2) 2*R2
+ - pin 6
R
R2
RNF
Figure 1
Error amp (channel 1) connection: Output voltage VO positive
VREF V0 - = - R R1 VREF * (R1 + R2) + VREF 2*R2
+ - pin 6
R
R2
RNF
V0 -
Figure 2
Error amp (channel 1) connection: Output voltage VO positive
8
MB3782
V0 + R1
V0 + =
1.25 * (R1 + R2) R2
+ - pin 12,17
R2
RNF
1.25 V
Figure 3 Error amp (channel 2, channel 3) connection
The non-inverting input to the error amps on channel 2 and channel 3 is internally connected to VREF/2, and therefore cannot be configured for inverting output. ch-1 Step up Step down Inverting x x ch-2 ch-3
9
MB3782
s USING THE RT PIN
The triangular waves, as shown in Figure 1, act to set the oscillator frequency by charging and discharging the capacitor connected to the CT pin using the current value of the resistor connected to the RT pin. In addition, when voltage level VREF/2 is output to external circuits from the RT pin, care must be taken in making the external circuit connections to adjust for the fact that I1 is increased by the value of the current I2 to the external circuits in determining the oscillator frequency (see Figure 2).
ICT = IRT Triangular wave oscillator = VREF 2RT
VREF 2 2 IRT RT CT 1 ICT
Figure 1
No VREF/2 connection to external circuits from RT pin
ICT = IRT Triangular wave generator = I1 + I2 VREF 2 2 IRT To external circuits IRT I1 RT CT 1 ICT = VREF + I2 2RT
Figure 2
VREF/2 connection to external circuits from RT pin
10
MB3782
s TREATMENT OF UNUSED ERROR AMPS
Any error amps that are not used should be handled as follows. Note that failure to apply proper treatment to error amps will cause the SCP circuit to activate and disable the switching regulator output.
1. Error Amp (channel 1) Not In Use
1 3 4 5 7 9
VREF RT + IN1 - IN1 DTC1 GND
Note: Pin 6 and pin 8 shoud be left open.
2. Error Amp (channel 2) Not In Use
1
VREF
9
- IN2 GND DTC2
13
11
Note: Pin 10 and pin 12 shoud be left open.
3. Error Amp (channel 3) Not In Use
VREF - IN3 18 DTC3 16
1
9
GND
Note: Pin 15 and pin 17 shoud be left open.
11
MB3782
s TREATMENT OF UNUSED SCP PIN
When the timer latch short protection circuit is not used, the SCP pin should be connected to the GND by the shortest possible path.
SCP
14
s ABSOLUTE MAXIMUM RATINGS
Parameter Power supply voltage Error amp input voltage Dead time control input voltage Control input voltage Collector output voltage Collector output current Allowable loss Operating temperature Storage temperature Symbol VCC VIN Vdt VCTL VOUT IOUT PD*1 Top Tstg Ta +25C Condition -- -- -- -- -- -- SOP Version DIP Version -- -- Rating 20 -0.3 to 10 -0.3 to 2.8 -0.3 to 20 20 75 740*2 1110 -30 to 85 -55 to 125 (Ta = +25C) Unit V V V V V mA mW C C
*1: For operation in conditions where Ta > +25C, the SOP version should be derated by 7.4 mW/C, and the DIP version should be derated by 11.1 mW/C. *2: When mounted on a 4 cm-square dual-sided epoxy board. Note: Permanent device damage may occur if the above Absolute Maximum Ratings are exceeded. Functional operation should be restricted to the conditions as detailed in the operational sections of this data sheet. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
12
MB3782
s RECOMMENDED OPERATING CONDITIONS
Parameter Power supply voltage Error amp input voltage Control input voltage Collector output voltage Collector output current Reference voltage output current Timing capacitance Timing resistance Oscillator frequency Operating temperature Symbol VCC VIN VCTL VOUT IOUT IREF CT RT fOSC Top Condition -- -- -- -- -- -- -- -- -- -- Value Min. 3.6 1.05 0 -- 0.3 -3 150 5.1 1 -30 Typical 6.0 -- -- -- -- -1 -- -- -- 25 Max. 18.0 1.45 18 18 50 0 15000 100 500 85 Unit V V V V mA mA pF k kHz C
13
MB3782
s ELECTRICAL CHARACTERISTICS
(VCC = 6 V, Ta = +25C) Parameter Reference voltage Output voltage Output voltage temperature variation Input stability Load stability Short output current Threshold voltage Hysteresis width Reset voltage (VCC) Input threshold voltage Input standby voltage Input latch voltage Input source current Comparator threshold voltage Oscillator frequency Frequency deviation Frequency deviation (VCC) Frequency deviation (Ta) Input threshold voltage ON duty cyclet Input bias current Latch mode sink current Latch input voltage Symbol VREF VRTC Line Load IOS VtH VtL VHYS VR VtPC VSTB VIN Ibpc VtC fOSC fdev fdV fdT Vt0 Vt100 Dtr Ibdt Idt Vdt Vdt = 2.5 V Idt = 100 A No pull-up No pull-up -- Pin 6, pin 12, pin 17 CT = 330 pF, RT = 15 k CT = 330 pF, RT = 15 k VCC = 3.6 to 18 V Ta = -30 to 85C Duty cycle = 0 % Duty cycle = 100 % Vdt = VR/1.45 V -- Conditions IOR = -1 mA Ta = -30 to 85C VCC = 3.6 to 18 V IOR = -0.1 to -1mA VREF = 2 V IOR = -0.1 mA IOR = -0.1 mA IOR = -0.1 mA -- -- Value Min. 2.45 -2 -- -- -30 -- -- 80 1.5 0.60 -- -- -1.4 -- 160 -- -- -4 1.05 -- 55 -- 150 -- Typ. 2.50 0.2 2 1 -10 2.72 2.60 120 1.9 0.65 50 50 -1.0 2.1 200 5 1 -- 1.3 1.9 65 0.2 500 -- Max. 2.55 2 10 7.5 -3 -- -- -- -- 0.70 100 100 -0.6 -- 240 -- -- +4 -- 2.25 75 1 -- 0.3 Unit V % mV mV mA V V mV V V mV mV A V kHz % % % V V % A A V
Dead time controller (DTC)
Triangular wave Short circuit protection Undervoltage lock oscillator (SCP) out circuit (UVLO)
(Continued)
14
MB3782
(Continued)
Parameter Input offset voltage Input offset current Input bias current Common mode input voltage range Error amps Voltage gain Frequency bandwidth Common mode rejection ratio Maximum output voltage range Output sink current Output source current PWM comparator Input threshold voltage Input sink current Input source current Input OFF conditions Input ON conditions Control pin current Output leak current Output saturation voltage Standby current Average feed current Symbol VIO IIO IB VICR Av BW CMRR VOM+ VOMIOM+ IOMVt0 Vt100 IIN+ IINVOFF VON ICTL Leak VSAT ICCS ICCa VCTL = 10 V VOUT = 18 V IOUT = 50 mA VCTL = 0 V VCTL = VCC, no output load VOUT = 1.6 V VOUT = 1.6 V Duty cycle = 0 % Duty cycle = 100 % Pin 6, pin 12, pin 17 Pin 6, pin 12, pin 17 -- -- Av = 0 dB -- -- -- Conditions VOUT = 1.6 V VOUT = 1.6 V VOUT = 1.6 V VCC = 3.6 to 18 V -- (VCC = 6 V, Ta = +25C) Value Unit Typ. Max. -- -- -100 -- 80 0.8 80 -- 0.7 1.0 -60 1.3 1.9 1.0 -60 -- -- 200 -- 1.1 -- 2.1 6 100 -- 1.45 -- -- -- -- 0.9 -- -- -- 2.25 -- -- 0.7 -- 400 10 1.4 10 3.2 mV nA nA V dB MHz dB V V mA A V V mA A V V A A V A mA
Min. -6 -100 -500 1.05 70 -- 60 VREF -0.3 -- -- -- 1.05 -- -- -- -- 2.1 -- -- -- -- --
Entire Output device block
Control block
* Voltage control on channel 1 may be positive or negative. * The non-inverting input to the error amps on channel 2 and channel 3 is internally connected to VREF/2, and therefore voltage control is positive only. * VREF/2 output can be obtained from the RT pin.
15
MB3782
s TEST CIRCUIT
OUTPUT OUTPUT 4.7 k 4.7 k VCC CTL
1 330 pF 2 150 k 3 4 5 TEST INPUT 7 8 9 10 6
20 19 18
4.7 k 17 16 15 14 CPF 13 12 11 TEST INPUT TEST INPUT OUTPUT
16
CT pin wavefoms
Short protection comparator reference input 2.1 V 1.9 V 1.6 V 1.3 V
Dead time,PWM input voltage Error amp output "High" "Low" "High" "Low" 0.6 V 0V "High" "Low" Power ON Power OFF tPE
PWM comparator output
Dead time 100 %
s TIMING CHART (INTERMAL WAVEFORMS)
Output transistor-collector waveforms
SCP pin waveforms
Short protection comparator output
2.1 V Control pin voltage (VCTL: minimum value) 0V 3.6 V 0V Protection enable time tPE 0.6 x 106 x CPE (s)
Power supply voltage (VCC: minimum)
MB3782
17
18
16 k 5.6 k 9.1 k
MB3782
1.8 k 1 F 1 F 4.7 k 2.4 k 10 k 4.7 k 10 k
s EXAMPLE OF APPLICATION
1 F 10 k
56 H
VIN (6 V)
CTL
1 7 11 16 20 19
VREF
4
DTC1 330
DTC2
DTC3 VCC
CTL 120 H 120 H 330 + 220 F -
10
+ IN1 - IN1 OUT1
8
4.7 k
5
V0 - (-5V)
0.033 F 150 k
6
FB1
330
1.8 k
13
- IN2 FB2 MB 3782
V0 + (+5V)
OUT2
0.033 F 150 k
12
1.8 k
18
330 120 H 220 F + - 3.9 k OUT3
15
- IN3 FB3 CT RT SCP GND
9
V0 + ( + 12 V )
0.033 F 150 k
17 2 3 14
820 PF
100
8.2 k
0.1 F
MB3782
s TYPICAL CHARACTERISTICS CURVES
Power supply voltage vs.reference voltage 5.0 Reference voltage VREF (V) 3.0 Power supply voltage vs.average feed current Ta = +25C
Ta = +25C
2.5
1.5
0 0 4 8 12 16 20 Power supply voltage VCC (V) Ambient temperature vs.reference voltage 2.51 2.50 2.49 2.48 2.47 1.2 2.46 2.45 - 40 1.0 0.8 - 20 0 20 40 60 80 Ambient temperature Ta (C) 100 VCC = VCTL = 6 V IOR = -1 mA
0 0 4 8 12 16 20 Power supply voltage VCC (V)
Timing capacity vs.triangular wave maximum amplitude voltage 2.2 2.0 1.8 1.6 1.4 VCC = 6 V RT = 15 k Ta = +25C
Reference voltage VREF (V)
102
103 Timihg capacitance CT (pF)
104
Sink current vs.collector saturation voltage Collector saturation voltagre VOL (V) 2.0 Error amp maximum output voltage amplitude (V) VCC = 6 V Ta = +25C 1.5
Frequency vs.error amp maximum output voltage amplitude 3.0 VCC = 6 V Ta = +25C 2.0
1.0
1.0
0.5
0 0 10 20 30 40 50 Sink current IOL (mA)
0 100
500 1 k
5 k 10 k Fequency f (Hz)
50 k 100 k
500 k
(Continued)
19
MB3782
Timing resistance vs.oscillator frequency VCC = 6 V Ta = +25C 100
Triangular wave period(sec)
Power supply voltage vs.averege feed current VCC = 6 V RT = 15 k Ta = +25C
1M
Oscillator frequency fOSC (Hz)
10
100 k CT = 150 pF
10 k CT = 15000 pF
CT = 1500 pF 1 102 103 104 105 Timing capacitance CT (pF)
1k 1k
5 k 10 k 50 k
100 k
500 k
Timing resistance RT () Ambient temperature vs.oscillator frequency 10
Frequency variation fDT (%)
Oscillator frequency vs.duty cycle 100
Duty Cycle Dtr (%)
VCC = 6 V CT = 330 pF RT = 15 k
80 60 40 20 0
VCC = 6 V CT = 1330 pF RT = 15 k Ta = +25C
0
- 10 - 40 - 20 0 20 40 60 80 100 120
5k
10 k
50 k
100 k
500 k 1 M
Oscillator frequency (Hz)
Ambient temperature Ta (C) Control voltage vs.reference voltage 5.0 VCC = 6 V CT = +25C 500
Control current ICTL (A)
Control input current VCC = 6 V CT = +25C
Reference voltage VREF (V)
2.5
250
0 0 1 2 3 4 5 Control voltage VCTL (V)
0 0 4 8 12 16 20 Control voltage VCTL (V)
(Continued)
20
MB3782
Frequenncy vs.gain and phase 40 20 CNF = open AV 180 90 0 - 90 40 20
Frequenncy vs.gain and phase CNF = 0.047 pF 180 AV 90 0 - 90
Phase (deg)
0
0
- 20 - 40 10 100 1k 10 k 100 k
- 20 - 40 10 100
- 180 1M
- 180 1k 10 k 100 k 1M
Frequenncy f (Hz) Frequenncy vs.gain and phase 40 20 CNF = 470 pF 180 90 0 - 90 40 20
Frequenncy f (Hz) Frequenncy vs.gain and phase CNF = 4700 pF AV 180 90 0 - 90
Phase (deg)
0 - 20 - 40 10 100 1k 10 k 100 k
0
- 20 - 40 10 100 1k 10 k 100 k
- 180 1M
- 180 1M
Frequenncy f (Hz) Test Circuit VREF VREF CNF
Frequenncy f (Hz)
4.7 k
4.7 k 240 k 4-
IN
10 F -+ 4.7 k 4.7 k
6 5+ Error amp
OUT
(Continued)
21
Phase (deg)
Gain AV (dB)
Gain AV (dB)
AV
Phase (deg)
Gain AV (dB)
Gain AV (dB)
MB3782
(Continued)
Ambient temperature vs.allowable loss
Allowable loss PD (mW)
1200 1110 1000 800 740 600 400 200
DIP version
SOP version
0 - 30 - 20 - 10 0
10 20 30 40 50 60 70 80 85
Ambient temperature Ta (C)
22
MB3782
s APPLICATIONS
3. Concerning Equivalent Series Resistance and Stability of Smoothing Capacitors
In DC/DC converters, the equivalent series resistance value (ESR) of smoothing capacitors has a major influence on loop phase characteristics. The ESR is a means by which phase characteristics approximate phase relationships to ideal capacitors in highfrequency bands (see Graph 1-1), thus improving system stability. At the same time, the use of smoothing capacitors with low ESR reduces system stability, so that care must be taken when using semiconductor electrolytic capacitors (OS capacitors) or tantalum capacitors with low ESR.
L Tr
Rc VIN D C
RL
Figure 1
Basic circuit for step-down voltage DC/DC converter
Frequency vs.Gain
Frequency vs.phase
20
0
0
Phase (deg)
Gain (dB)
2 - 90
- 20
2
- 40 1 : Rc = 0 - 60 10 2 : Rc = 31 m 1 - 180
1 : Rc = 0 2 : Rc = 31 m
1
100
1k Frequency f (Hz)
10 k
100 k
10
100
1k Frequency f (Hz)
10 k
100 k
Graph 1
Frequency vs. gain and phase
23
MB3782
* Reference data Changing the smoothing capacitor from an aluminum electrolytic capacitor (RC 1.0) to a lower-ESR semiconductor electrolytic capacitor (OS capacitor: RC 0.2 ) decreases the phase margin (see Graphs 1-2, 1-3).
V out V0 +
CNF AV and phase characteristics measured between these points - IN FB - + + IN R1 R2 VIN
VREF/2 Error amp
Figure 2
Measurement of DC/DC Capacitor AV and Phase () Characteristics
Graph
60 40
DC/DC converter + 5 V output frequency vs.gain and phase Vcc = 10 v RL = 25 Cp = 0.1 F 62
180 V0 +
Av
Gain (dB)
20 0 - 20 - 40 10
Phase (deg)
90 0 - 90
+ -
Aluminum electrolytic capacitor 220 F (16 V) RC 1.0 : fosc = 1 kHz
100
1k Frequency f (Hz)
10 k
- 180 100 k
Graph 3
60 40
Gain (dB)
DC/DC converter + 5 V output frequency vs.gain and phase Vcc = 10 v RL = 25 Cp = 0.1 F
Av
180 90
Phase (deg)
20 0 - 20 - 40 10 27
0 - 90
+ -
OS capacitor 22 F (16 V) RC 0.2 : fosc = 1 kHz
100
1k Frequency f (Hz)
10 k
- 180 100 k
24
MB3782
s ORDERING INFORMATION
Part number MB3782P MB3782PF Package Plastic DIP, 20 pin (DIP-20P-M01) Plastic SOP, 20 pin (FPT-20P-M01) Remarks
25
MB3782
s PACKAGE DIMENSIONS
Plastic DIP 20 pin , (DIP-20P-M01)
24.64 -0.30 .970 -.012
+.008 +0.20
INDEX-1 INDEX-2 6.600.25 (.260.010)
4.36(.172)MAX
0.51(.020)MIN 0.250.05 (.010.002)
3.00(.118)MIN
0.460.08 (.018.003)
+0.30 +.012 -0 +0.30 +.012 -0
0.86 -0 .034 1.27(.050) MAX
1.27 -0
.050 2.54(.100) TYP
7.62(.300) TYP
15MAX
Dimensions in mm (inches)
C
1994 FUJITSU LIMITED D20005S-3C-3
(Continued)
26
MB3782
(Continued)
Plastic SOP, 20 pin (FPT-20P-M01)
2.25(.089)MAX 12.70
+0.25 -0.20 +.010 -.008
.500
0.05(.002)MIN (STAND OFF)
INDEX
5.300.30 (.209.012)
7.800.40 (.307.016)
6.80 -0.20 +.016 .268 -.008
+0.40
1.27(.050) TYP
0.450.10 (.018.004)
O0.13(.005)
M
0.15 -0.02 +.002 .006 -.001
+0.05
0.500.20 (.020.008)
Details of "A" part 0.20(.008)
"A" 0.10(.004) 11.43(.450)REF 0.50(.020) 0.18(.007)MAX 0.68(.027)MAX
C
1994 FUJITSU LIMITED F20003S-5C-4
Dimensions in mm (inches)
27
MB3782
FUJITSU LIMITED
For 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: (044) 754-3763 Fax: (044) 754-3329
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 and circuit diagrams in this document presented as examples of semiconductor device applications, and are not intended to be incorporated in devices for actual use. Also, FUJITSU is unable to assume responsibility for infringement of any patent rights or other rights of third parties arising from the use of this information or circuit diagrams. FUJITSU semiconductor devices are intended for use in standard applications (computers, office automation and other office equipment, industrial, communications, and measurement equipment, personal or household devices, etc.). CAUTION: Customers considering the use of our products in special applications where failure or abnormal operation may directly affect human lives or cause physical injury or property damage, or where extremely high levels of reliability are demanded (such as aerospace systems, atomic energy controls, sea floor repeaters, vehicle operating controls, medical devices for life support, etc.) are requested to consult with FUJITSU sales representatives before such use. The company will not be responsible for damages arising from such use without prior approval. Any semiconductor devices have inherently a certain rate 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 Control Law of Japan, the prior authorization by Japanese government should be required for export of those products from Japan.
http://www.fujitsu.co.jp/
North and South America FUJITSU MICROELECTRONICS, INC. Semiconductor Division 3545 North First Street San Jose, CA 95134-1804, USA Tel: (408) 922-9000 Fax: (408) 922-9179 Customer Response Center Mon. - Fri.: 7 am - 5 pm (PST) Tel: (800) 866-8608 Fax: (408) 922-9179
http://www.fujitsumicro.com/
Europe FUJITSU MIKROELEKTRONIK GmbH Am 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 PTE LTD #05-08, 151 Lorong Chuan New Tech Park Singapore 556741 Tel: (65) 281-0770 Fax: (65) 281-0220
http://www.fmap.com.sg/
F9803 (c) FUJITSU LIMITED Printed in Japan
28

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