Fujitsu MB3782P Switching regulator controller Datasheet

FUJITSU SEMICONDUCTOR
DATA SHEET
DS04-27205-4E
ASSP Power Supplies
BIPOLAR
Switching Regulator Controller
MB3782
■ 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 µA), 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.
■ FEATURES
•
•
•
•
•
•
•
•
Wide voltage range (3.6 to 18 V)
Low power dissipation (operating mode: 2.1 mA (typ), standby mode: 10 µA (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)
■ PACKAGE
Plastic DIP, 20 pin
Plastic SOP, 20 pin
(DIP-20P-M01)
(FPT-20P-M01)
MB3782
■ PIN ASSIGNMENT
TOP VIEW
VREF
1
20
VCC
CT
2
19
CTL
RT
3
18
– IN3
+ IN1
4
17
FB3
– IN1
5
16
DTC3
FB1
6
15
OUT3
DTC1
7
14
SCP
PUT1
8
13
– IN2
GND
9
12
FB2
OUT2
10
11
DTC2
(DIP-20P-M01)
(FPT-20P-M01)
■ PIN DESCRIPTION
Pin No.
Pin Name
I/O
Description
1
VREF
O
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.
2
CT
—
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 kΩ. This pin can also provide
output at voltage level VREF/2, for use as error amplifier
reference input.
3
RT
—
4
+IN1
I
Error amplifier 1 non-inverting input pin.
5
–IN1
I
Error amplifier 1 inverting input pin.
6
FB1
O
Error amplifier 1 output pin: connect resistor and capacitor
between this pin and the –IN1 pin to set gain and adjust
frequency characteristics.
I
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.
7
DTC1*
1
(Continued)
2
MB3782
(Continued)
Pin No.
Pin Name
I/O
Description
8
VOUT1
O
Open collector type output pin with an emitter connected to
GND.
Output current may be up to 50 mA.
9
GND
—
Ground pin
10
OUT2
O
Open collector type output pin with an emitter connected to
GND. Output current may be up to 50 mA.
11
DTC2*1
I
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.
12
FB2
O
Error amplifier 2 output pin: connect resistor and capacitor
between this pin and the –IN2 pin to set gain and adjust
frequency characteristics.
13
–IN2
I
Error amplifier 2 inverting input pin.
14
SCP*2
—
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 “■ Setting
the Time Constant for the Timer-Latch Type Short Prevention
Circuit.”
15
OUT3
O
Open collector type output pin for emitter connected to GND.
Output current may be up to 50 mA.
I
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.
1
16
DTC3*
17
FB3
O
Error amplifier 3 output pin: connect resistor and capacitor
between this pin and the –IN3 pin to set gain and adjust
frequency characteristics.
18
–IN3
I
Error amplifier 3 inverting input pin.
19
CTL
I
Power supply control pin: low level places the IC in standby
mode and reduces power consumption to 10 µA or lower. Input
level may be driven by TTL or CMOS.
20
VCC
—
Power supply pin: voltage range is 3.6 to 18 V.
(Continued)
*1: DTC = Dead Time Control
*2: SCP = Short Circuit Protection
3
MB3782
■ BLOCK DIAGRAM
RT
CT
VREF
VCC
CLT
3
2
1
20
19
1.25 V
2.5 V
Reference
voltage
source
Triangular wave
oscillator
Error Amp.1
+ IN1
4
– IN1
5
FB1
6
DTC1
7
– IN2
13
Power on/off
control
circuit
9
GND
8
OUT1
10
OUT2
15
OUT3
PWM Comp.
Ch.1
+
+
+
–
–
Error Amp.2
PWM Comp.
–
Ch.2
+
+
–
+
1.25 V
FB2
DTC2
12
– IN3
18
11
Error Amp.3
PWM Comp.
–
+
+
–
+
1.25 V
FB3
17
DTC3
16
SCP Comp.
–
–
–
+
2.1 V
VREF
1 µA
SCP
14
S
R
Latch
4
U.V.L.O.
Ch.3
MB3782
■ 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 µA or less.)
6
MB3782
■ 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 C PE externally connected to the SCP pin voltage is then charged according to the following formulas.
VPE = 50 mV + tPE × 10–6/CPE
0.65 = 50 mV + tPE × 10–6/CPE
CPE = tPE/0.6 (µF)
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 C PE
2.50 V
1 µA
S.C.P.Comp.
Error Amp.1
Error Amp.2
Error Amp.3
–
–
–
+
14
CPE
Q1
Q3
S
PWM
Comp.
R
Latch
Out
U.V.L.O.
2.1 V
Figure 1
Protection Latch Circuit
7
MB3782
■ 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
V0 + =
VREF
· (R1 + R2)
2·R2
R1
+
pin 6
–
R
Figure 1
R2
RNF
Error amp (channel 1) connection: Output voltage VO positive
VREF
V0 – = –
R
VREF
· (R1 + R2) + VREF
2·R2
R1
+
pin 6
–
R
R2
RNF
V0 –
Figure 2
8
Error amp (channel 1) connection: Output voltage VO positive
MB3782
V0 +
V0 + =
1.25
· (R1 + R2)
R2
R1
+
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
ch-2
ch-3
×
×
Step up
Step down
Inverting
9
MB3782
■ 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
1
IRT
ICT
CT
RT
Figure 1
No VREF/2 connection to external circuits from RT pin
ICT = IRT
Triangular wave generator
= I1 + I2
=
VREF
2
2
VREF
+ I2
2RT
1
IRT
ICT
To external circuits
IRT
I1
RT
Figure 2
10
CT
VREF/2 connection to external circuits from RT pin
MB3782
■ 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
VREF
3
5
RT
+ IN1
– IN1
7
DTC1
9
GND
4
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
1
VREF
– IN3 18
DTC3 16
9
GND
Note: Pin 15 and pin 17 shoud be left open.
11
MB3782
■ 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
■ ABSOLUTE MAXIMUM RATINGS
Parameter
(Ta = +25°C)
Unit
Symbol
Condition
Rating
Power supply voltage
VCC
—
20
V
Error amp input voltage
VIN
—
–0.3 to 10
V
Dead time control input voltage
Vdt
—
–0.3 to 2.8
V
Control input voltage
VCTL
—
–0.3 to 20
V
Collector output voltage
VOUT
—
20
V
Collector output current
IOUT
—
75
mA
Allowable loss
P D*1
Operating temperature
Top
—
–30 to 85
°C
Storage temperature
Tstg
—
–55 to 125
°C
Ta ≤ +25°C
SOP Version
740*2
DIP Version
1110
mW
*1: For operation in conditions where Ta > +25°C, 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
■ RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Condition
Power supply voltage
VCC
Error amp input voltage
Value
Unit
Min.
Typical
Max.
—
3.6
6.0
18.0
V
VIN
—
1.05
—
1.45
V
Control input voltage
VCTL
—
0
—
18
V
Collector output voltage
VOUT
—
—
—
18
V
Collector output current
IOUT
—
0.3
—
50
mA
Reference voltage output current
IREF
—
–3
–1
0
mA
Timing capacitance
CT
—
150
—
15000
pF
Timing resistance
RT
—
5.1
—
100
kΩ
Oscillator frequency
fOSC
—
1
—
500
kHz
Operating temperature
Top
—
–30
25
85
°C
13
MB3782
■ ELECTRICAL CHARACTERISTICS
(VCC = 6 V, Ta = +25°C)
Dead time controller
(DTC)
Triangular wave Short circuit protection Undervoltage lock
oscillator
(SCP)
out circuit (UVLO)
Reference voltage
Parameter
Symbol
Conditions
Value
Unit
Min.
Typ.
Max.
2.45
2.50
2.55
V
Output voltage
VREF
IOR = –1 mA
Output voltage
temperature variation
VRTC
Ta = –30 to 85°C
–2
±0.2
2
%
Input stability
Line
VCC = 3.6 to 18 V
—
2
10
mV
Load stability
Load
IOR = –0.1 to –1mA
—
1
7.5
mV
–30
–10
–3
mA
Short output current
Threshold voltage
Hysteresis width
Reset voltage (VCC)
IOS
VREF = 2 V
VtH
IOR = –0.1 mA
—
2.72
—
V
VtL
IOR = –0.1 mA
—
2.60
—
V
VHYS
IOR = –0.1 mA
80
120
—
mV
VR
—
1.5
1.9
—
V
Input threshold voltage
VtPC
—
0.60
0.65
0.70
V
Input standby voltage
VSTB
No pull-up
—
50
100
mV
Input latch voltage
VIN
No pull-up
—
50
100
mV
Input source current
Ibpc
–1.4
–1.0
–0.6
µA
Comparator threshold
voltage
VtC
Pin 6, pin 12, pin 17
—
2.1
—
V
Oscillator frequency
fOSC
CT = 330 pF, RT = 15 kΩ
160
200
240
kHz
Frequency deviation
fdev
CT = 330 pF, RT = 15 kΩ
—
±5
—
%
Frequency deviation (VCC)
fdV
VCC = 3.6 to 18 V
—
±1
—
%
Frequency deviation (Ta)
fdT
Ta = –30 to 85°C
–4
—
+4
%
Vt0
Duty cycle = 0 %
1.05
1.3
—
V
Duty cycle = 100 %
—
1.9
2.25
V
Vdt = VR/1.45 V
55
65
75
%
—
0.2
1
µA
Input threshold voltage
Vt100
—
ON duty cyclet
Dtr
Input bias current
Ibdt
Latch mode sink current
Idt
Vdt = 2.5 V
150
500
—
µA
Latch input voltage
Vdt
Idt = 100 µA
—
—
0.3
V
—
(Continued)
14
MB3782
(Continued)
Parameter
Error amps
PWM
comparator
Control
block
Conditions
Min.
Input offset voltage
VIO
VOUT = 1.6 V
–6
—
6
mV
Input offset current
IIO
VOUT = 1.6 V
–100
—
100
nA
Input bias current
IB
VOUT = 1.6 V
–500
–100
—
nA
VCC = 3.6 to 18 V
1.05
—
1.45
V
70
80
—
dB
—
0.8
—
MHz
Common mode input
voltage range
Entire Output
device block
Symbol
(VCC = 6 V, Ta = +25°C)
Value
Unit
Typ. Max.
VICR
Voltage gain
Av
Frequency bandwidth
BW
Common mode rejection
ratio
—
Av = 0 dB
CMRR
—
60
80
—
dB
Maximum output voltage
range
VOM+
—
VREF
–0.3
—
—
V
VOM-
—
—
0.7
0.9
V
Output sink current
IOM+
VOUT = 1.6 V
—
1.0
—
mA
Output source current
IOM-
VOUT = 1.6 V
—
–60
—
µA
Vt0
Duty cycle = 0 %
1.05
1.3
—
V
Input threshold voltage
Vt100
Duty cycle = 100 %
—
1.9
2.25
V
Input sink current
IIN+
Pin 6, pin 12, pin 17
—
1.0
—
mA
Input source current
IIN-
Pin 6, pin 12, pin 17
—
–60
—
µA
Input OFF conditions
VOFF
—
—
—
0.7
V
Input ON conditions
VON
—
2.1
—
—
V
Control pin current
ICTL
VCTL = 10 V
—
200
400
µA
Output leak current
Leak
VOUT = 18 V
—
—
10
µA
Output saturation voltage
VSAT
IOUT = 50 mA
—
1.1
1.4
V
Standby current
ICCS
VCTL = 0 V
—
—
10
µA
Average feed current
ICCa
VCTL = VCC, no output load
—
2.1
3.2
mA
• 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
■ TEST CIRCUIT
OUTPUT
OUTPUT
4.7 kΩ
4.7 kΩ
1
20
2
19
3
18
4
17
TEST
5
16
INPUT
6
15
7
14
8
13
9
12
TEST
10
11
INPUT
VCC
330 pF
CTL
150 kΩ
4.7 kΩ
TEST
OUTPUT
INPUT
CPF
16
“Low”
“High”
0V
0.6 V
“Low”
“High”
“Low”
“High”
2.1 V
1.9 V
1.6 V
1.3 V
Power supply voltage (VCC: minimum)
0V
3.6 V
2.1 V
Control pin voltage (VCTL: minimum value)
0V
Short protection comparator output
SCP pin waveforms
Output transistor-collector waveforms
PWM comparator output
Error amp output
Dead time,PWM input voltage
Short protection comparator reference input
CT pin wavefoms
Power ON
Protection enable time tPE ≅ 0.6 × 106 × CPE (µs)
Power OFF
tPE
Dead time 100 %
MB3782
■ TIMING CHART (INTERMAL WAVEFORMS)
17
18
CTL
VIN (6 V)
0.1 µF
8.2 kΩ
820 PF
1.8 kΩ
1.8 kΩ
4.7 kΩ
0.033 µF
0.033 µF
0.033 µF
56 µH
13
6
5
150 kΩ
RT
SCP
14
CT
2
3
FB3
– IN3
FB2
– IN2
FB1
– IN1
+ IN1
17
18
12
150 kΩ
150 kΩ
4
1.8 kΩ
MB 3782
11
DTC2
7
DTC1
1
2.4 kΩ
10 kΩ
4.7 kΩ
10 kΩ
VREF
4.7 kΩ
1 µF
1 µF
1 µF
20
DTC3 VCC
16
10 kΩ
GND
OUT3
OUT2
OUT1
CTL
19
9.1 kΩ
5.6 kΩ
16 kΩ
9
15
10
8
3.9 kΩ
100 Ω
330 Ω
120 µH
330 Ω
330 Ω
330 Ω
120 µH
220 µF +
–
+
220 µF –
120 µH
V0 +
( + 12 V )
V0 +
(+5V)
V0 –
(–5V)
MB3782
■ EXAMPLE OF APPLICATION
MB3782
■ TYPICAL CHARACTERISTICS CURVES
Power supply voltage vs.reference voltage
Reference voltage VREF (V)
5.0
Power supply voltage vs.average feed current
3.0
Ta = +25°C
Ta = +25°C
1.5
2.5
0
0
0
4
8
12
16
0
20
4
8
12
16
20
Power supply voltage VCC (V)
Power supply voltage VCC (V)
Ambient temperature vs.reference voltage
Timing capacity vs.triangular wave maximum amplitude voltage
VCC = VCTL = 6 V
IOR = –1 mA
2.50
2.2
VCC = 6 V
RT = 15 kΩ
Ta = +25°C
2.0
2.49
1.8
2.48
1.6
1.4
2.47
1.2
2.46
1.0
2.45
– 40
0.8
– 20
0
20
40
60
80
Ambient temperature Ta (°C)
100
103
102
104
Timihg capacitance CT (pF)
Sink current vs.collector saturation voltage
2.0
VCC = 6 V
Ta = +25°C
1.5
1.0
0.5
0
0
10
20
30
40
50
Error amp maximum output voltage amplitude (V)
Collector saturation voltagre VOL (V)
Reference voltage VREF (V)
2.51
Frequency vs.error amp maximum output voltage amplitude
3.0
VCC = 6 V
Ta = +25°C
2.0
1.0
0
100
500 1 k
5 k 10 k
50 k 100 k
500 k
Fequency f (Hz)
Sink current IOL (mA)
(Continued)
19
MB3782
Timing resistance vs.oscillator frequency
VCC = 6 V
Ta = +25°C
Power supply voltage vs.averege feed current
100
Triangular wave period(µsec)
Oscillator frequency fOSC (Hz)
1M
100 k
CT = 150 pF
10 k
VCC = 6 V
RT = 15 kΩ
Ta = +25°C
10
CT = 1500 pF
1
102
CT = 15000 pF
103
104
105
Timing capacitance CT (pF)
1k
1k
5 k 10 k 50 k
100 k
500 k
Timing resistance RT (Ω)
Ambient temperature vs.oscillator frequency
Oscillator frequency vs.duty cycle
100
VCC = 6 V
CT = 330 pF
RT = 15 kΩ
0
Duty Cycle Dtr (%)
Frequency variation fDT (%)
10
VCC = 6 V
CT = 1330 pF
RT = 15 kΩ
Ta = +25°C
80
60
40
20
0
– 10
– 40
– 20
0
20
40
60
80
100
5k
120
10 k
50 k
100 k
500 k 1 M
Oscillator frequency (Hz)
Ambient temperature Ta (°C)
Control input current
VCC = 6 V
CT = +25°C
5.0
VCC = 6 V
CT = +25°C
500
Control current ICTL (µA)
Reference voltage VREF (V)
Control voltage vs.reference voltage
2.5
0
250
0
0
1
2
3
Control voltage VCTL (V)
4
5
0
4
8
12
16
20
Control voltage VCTL (V)
(Continued)
20
MB3782
Frequenncy vs.gain and phase
Frequenncy vs.gain and phase
20
0
φ
– 20
– 90
– 40
– 180
100
1k
10 k
100 k
0
φ
– 20
– 90
1M
– 180
10
100
1k
10 k
100 k
Frequenncy f (Hz)
Frequenncy vs.gain and phase
Frequenncy vs.gain and phase
CNF = 470 pF
20
Gain AV (dB)
0
Frequenncy f (Hz)
40
AV
0
180
40
90
20
0
φ
– 20
– 90
– 40
10
90
– 40
Phase ϕ (deg)
10
AV
– 180
100
1k
10 k
100 k
1M
Phase ϕ (deg)
90
CNF = 0.047 pF 180
1M
CNF = 4700 pF
AV
180
90
0
0
φ
Phase ϕ (deg)
0
40
Gain AV (dB)
Gain AV (dB)
20
180
Gain AV (dB)
AV
Phase ϕ (deg)
CNF = open
40
– 20
– 90
– 40
– 180
10
100
Frequenncy f (Hz)
1k
10 k
100 k
1M
Frequenncy f (Hz)
Test Circuit
VREF
VREF
CNF
4.7 kΩ
4.7 kΩ
240 kΩ
4 –
IN
10 µF
– +
4.7 kΩ
6
OUT
5 +
4.7 kΩ
Error amp
(Continued)
21
MB3782
(Continued)
Allowable loss PD (mW)
Ambient temperature vs.allowable loss
1200
1110
1000
DIP version
800
740
600
SOP version
400
200
0
– 30 – 20 – 10 0
10 20 30 40 50 60 70 80 85
Ambient temperature Ta (°C)
22
MB3782
■ 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
RL
C
Figure 1
Basic circuit for step-down voltage DC/DC converter
Frequency vs.phase
Frequency vs.Gain
0
20
– 20
Phase (deg)
Gain (dB)
0
2
2
– 90
– 40
1 : Rc = 0 Ω
1 : Rc = 0 Ω
– 60
10
1
2 : Rc = 31 mΩ
100
1k
10 k
– 180
100 k
10
100
Frequency f (Hz)
Graph 1
1
2 : Rc = 31 mΩ
1k
10 k
100 k
Frequency f (Hz)
Frequency vs. gain and phase
23
MB3782
• Reference data
Changing the smoothing capacitor from an aluminum electrolytic capacitor (RC ≅ 1.0Ω) to a lower-ESR
semiconductor electrolytic capacitor (OS capacitor: RC ≅ 0.2 Ω) 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
+
VIN
R2
R1
VREF/2
Error amp
Figure 2
Measurement of DC/DC Capacitor AV and Phase (Ψ) Characteristics
DC/DC converter + 5 V output frequency vs.gain and phase
Graph
60
Vcc = 10 v
RL = 25 Ω
Cp = 0.1 µF
Gain (dB)
Av
180
V0 +
φ
20
90
62°
0
0
+
–
Aluminum electrolytic
capacitor
220 µF (16 V)
RC ≅ 1.0 Ω
: fosc = 1 kHz
– 90
– 20
– 40
10
Phase (deg)
40
100
1k
– 180
100 k
10 k
Frequency f (Hz)
Graph 3
DC/DC converter + 5 V output frequency vs.gain and phase
60
90
20
φ
0
27°
– 40
10
0
– 90
– 20
100
1k
Frequency f (Hz)
24
180
Phase (deg)
40
Gain (dB)
Vcc = 10 v
RL = 25 Ω
Cp = 0.1 µF
Av
10 k
– 180
100 k
+
–
OS capacitor
22 µF (16 V)
RC ≅ 0.2 Ω
: fosc = 1 kHz
MB3782
■ ORDERING INFORMATION
Part number
Package
MB3782P
Plastic DIP, 20 pin
(DIP-20P-M01)
MB3782PF
Plastic SOP, 20 pin
(FPT-20P-M01)
Remarks
25
MB3782
■ PACKAGE DIMENSIONS
Plastic DIP, 20 pin
(DIP-20P-M01)
+0.20
24.64 –0.30
+.008
.970 –.012
INDEX-1
6.60±0.25
(.260±.010)
INDEX-2
0.51(.020)MIN
4.36(.172)MAX
0.25±0.05
(.010±.002)
3.00(.118)MIN
0.46±0.08
(.018±.003)
+0.30
0.86 –0
.034
+.012
–0
1.27(.050)
MAX
+0.30
1.27 –0
+.012
–0
.050
2.54(.100)
TYP
7.62(.300)
TYP
15°MAX
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
.500
+.010
–.008
0.05(.002)MIN
(STAND OFF)
5.30±0.30
(.209±.012)
INDEX
1.27(.050)
TYP
0.45±0.10
(.018±.004)
+0.40
6.80 –0.20
+.016
.268 –.008
7.80±0.40
(.307±.016)
+0.05
Ø0.13(.005)
M
0.15 –0.02
+.002
.006 –.001
0.50±0.20
(.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
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
 FUJITSU LIMITED Printed in Japan
28
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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.
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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.
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