FUJITSU MB3821PFV

FUJITSU SEMICONDUCTOR
DATA SHEET
DS04-27221-2E
ASSP For Power Supply Applications
With Power Mode Switching Function
2-ch DC/DC Converter IC With Synchronous Rectifier
MB3821
■ DESCRIPTION
The MB3821 is a pulse width modulation (PWM) type 2-channel DC/DC converter IC with synchronous rectification
designed for low voltage, high efficiency operation in high precision and high frequency applications, ideal for down
conversion.
A normal/low-power mode selection is provided, ideal for an internal power supply (3.3V, 5V) in applications with
substantial load current variation, such as notebook computers.
■ FEATURES
• Synchronous rectification
• High efficiency
: 93 % (normal power mode, VIN = 6 V, load 1 A)
: 84 % (low power mode, VIN = 6 V, load 20 mA)
•
•
•
•
•
Built-in power mode selector circuit
Reference voltage accuracy : 2.5V ± 2 %
Built-in error amp input control type soft start circuit
Totem pole type output for N-ch MOSFET applications
Built-in timer-latch type short protection circuit
■ PACKAGE
24-pin, Plastic SSOP
(FPT-24P-M03)
MB3821
■ PIN ASSIGNMENT
(TOP VIEW)
CT : 1
24 : VREF
RT : 2
23: VCC
GND : 3
IN
(CH1)
22 : CSCP
CS1 : 4
21 : CS2
−IN1 : 5
20 : −IN2
FB1 : 6
19 : FB2
SEL : 7
18 : CTL
OUT1−1 : 8
OUT
(CH2)
17 : OUT1−2
VS1 : 9
16 : VS2
CB1 : 10
15 : CB2
OUT2−1 : 11
14: OUT2−2
GND(0) : 12
13 :VB
(FPT-24P-M03)
2
IN
OUT
MB3821
■ PIN DESCRIPTION
Pin No.
Symbol
I/O
Descriptions
1
CT
—
Triangular wave oscillator frequency setting capacitance connection pin.
2
RT
—
Triangular wave oscillator frequency setting resistance connection pin.
3
GND
—
Ground pin.
4
CS1
—
Capacitor connection pin for Channel 1 soft start (also channel control).
5
–IN1
I
Channel 1 error amplifier inverted input pin.
6
FB1
O
Channel 1 error amplifier output pin
7
SEL
I
Mode select pin. Set the SEL pin to “H” level to switch the IC to low power mode.
8
OUT1-1
I
Totem pole type output pin (external main side FET gate drive).
9
VS1
—
Channel 1 external main side FET source connection pin.
10
CB1
—
Channel 1 boot capacitance connection pin.
11
OUT2-1
O
Channel 1 totem pole output pin (external main side FET gate drive).
12
GND(0)
—
Ground pin for output circuit.
13
VB
—
Power supply pin for output circuit.
14
OUT2-2
O
Channel 2 totem pole output pin (external synchronous rectifier side FET gate
drive).
15
CB2
—
Channel 2 boot capacitance connection pin.
16
VS2
—
Channel 2 external main side FET source connection pin.
17
OUT1-2
O
Channel 2 totem pole output pin (external main side FET gate drive).
18
CTL
I
Power supply control pin. Set CTL pin to “L” to switch the IC to standby mode.
19
FB2
O
Channel 2 error amplifier output pin.
20
–IN2
I
Channel 2 error amplifier inverted input pin.
21
CS2
—
Channel 2 soft start capacitance connection pin(also channel control).
22
CSCP
—
Timer-latch short circuit protection capacitance connection pin.
23
VCC
—
Reference power supply, control circuit power supply pin.
24
VREF
O
Reference voltage output pin.
3
MB3821
■ BLOCK DIAGRAM
1 µΑ 1 µΑ
13 VB
10 CB1
FB1 6
Error Amp.
PWM Comp.1
−
+
+
−IN1 5
CS1 4
23 VCC
+
8 OUT1−1
Drive
−
1.26 V
9 VS1
PWM Comp.2
(40 mV)
+
−
11 OUT2−1
Drive
< CH1 >
15 CB2
FB2 19
Error Amp.
PWM Comp.1
−
+
+
−IN2 20
CS2 21
+
17 OUT1−2
Drive
−
1.26 V
16 VS2
PWM Comp.2
(40 mV)
+
−
14 OUT2−2
Drive
< CH2 >
SCP Comp.
1 µΑ
12 GND (0)
−
−
+
1.9 V
2.1 V
1.3 V
bias
bias
CSCP 22
S
R
Latch
UVLO
7
SEL
4
Ref
Power
(2.5 V) ON/OFF
OSC
1
CT
2
RT
24
VREF
3
GND
18 CTL
MB3821
■ ABSOLUTE MAXIMUM RAGINGS
Parameter
Symbol
Conditions
Power supply voltage
VCC
Bias voltage
Rating
Unit
Min.
Max.
—
—
32
V
VB
—
—
17
V
Output current
Io
—
—
50
mA
Output peak current
Io
Duty ≤ 5 %
—
500
mA
Power dissipation
PD
Ta ≤ +25°C
—
740*
mW
Storage temperature
Tstg
−55
+125
°C
—
* : The packages are mounted on the epoxy board (10 cm × 10 cm).
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
Parameter
Symbol
Conditions
Power supply voltage
VCC
Bias voltage
Value
Unit
Min.
Typ.
Max.
—
4.5
16
30
V
VB
—
—
6
16
V
Reference voltage output current
IOR
—
–1
—
0
mA
Input voltage
VIN
-IN pin
0
—
VCC – 1.8
V
SEL, CTL pin
0
—
30
V
Output current
IO
OUT pin
–30
—
30
mA
Output peak current
Io
Duty ≤ 5 %
–300
—
300
mA
Timing capacitance
CT
—
150
500
15000
pF
Timing resistance
RT
—
6.8
10
12
kΩ
Oscillator frequency
fOSC
SEL = 0 V (Normal mode)
10
200
500
kHz
SEL = 5 V (Low power mode)
1
20
50
kHz
Soft-start capacitance
CS
—
—
0.1
1.0
µF
CSCP
—
—
0.01
1.0
µF
Boot capacitance
CB
—
—
0.1
1.0
µF
Operating ambient temperature
Ta
—
–30
+25
+85
°C
Short detection capacitance
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.
5
MB3821
■ ELECTRICAL CHARACTERISTICS
Short circuit
detection block
Soft-start
block
Under voltage
lockout protection
circuit block(U.V.L.O)
Reference
voltage
block
(VCC = 16 V, SEL =0 V, Ta = +25°C)
Parameter
Symbol
Pin
No.
Output voltage
VREF
24
VREF =0 mA
Output voltage
temperature variation
∆VREF
/VREF
24
Input stability
Line
Load stability
Value
Unit
Min.
Typ.
Max.
2.45
2.50
2.55
V
Ta = –30°C to +85°C
—
0.5*
—
%
24
VCC = 4.5 V to 30 V
—
—
15
mV
Load
24
VREF = 0 mA to –1.0 mA
—
—
15
mV
Short-circuit output
current
IOS
24
VREF = 1 V
–60
–25
—
mA
Threshold voltage
VTH
4,21 VCC =
3.2
3.5
3.8
V
Hysteresis width
VH
4,21
—
—
0.18
—
V
Reset voltage
VRST
4,21
—
2.4
2.8
—
V
Charge current
ICS
4,21
—
–1.4
–1.0
–0.6
µA
Input standby voltage
VSTB
4,21
—
—
50
100
mV
Threshold voltage
VTH
4,21
—
0.63
0.68
0.73
V
Input source current
ICSCP
22
—
–1.4
–1.0
–0.6
µA
Short detection time
tSCP
22
4.5
6.8
12.2
ms
Input standby voltage
VSTB
22
—
—
50
100
mV
VI
22
—
—
50
100
mV
SEL = 0 V
180
200
220
kHz
SEL = 5 V
16
20
24
kHz
Input latch voltage
Oscillator frequency
Triangular
wave oscillator
block
Conditions
Mode select voltage
Input current
fOSC
CSCP = 0.01 µF
8,11, CT = 500pF,
14,17 RT = 10 kΩ
VLOW
7
Low power mode
2.0
—
—
V
VHI
7
Normal mode
—
—
1.0
V
ISEL
7
SEL = 5 V
—
50
80
µA
SEL = 0 V
—
1
10
%
Frequency stability for
voltage
∆f/fdv
CT = 500pF,
8,11,
RT = 10 kΩ
14,17
VCC = 4.5V to 30V
SEL = 5 V
—
1
10
%
Frequency stability for
temperature
∆f/fdt
CT = 500pF,
SEL = 0 V
8,11,
RT = 10 kΩ
14,17
Ta = –30°C to +85°C SEL = 5 V
—
1*
—
%
—
1*
—
%
*: Standard design value.
(Continued)
6
MB3821
(Continued)
(VCC = 16 V, SEL =0 V, Ta = +25°C)
Error amplifier block
Parameter
PWM
Comp.
block
Dead time
control block
Output block
(Drive)
Conditions
VTH
6,19 FB = 1.6 V
VT temperature stability
∆VT
/VT
6,19 Ta = –30°C to +85°C
Value
Unit
Min.
Typ.
Max.
1.235
1.260
1.285
V
—
0.5*
—
%
–200
–50
—
nA
Input bias current
IB
5,20 −IN = 0 V
Voltage gain
AV
6,19 DC
60
100
—
dB
Frequency bandwidth
BW
6,19 AV = 0 dB
—
800*
—
kHz
VOH
6,19
—
VREF –
0.3
—
—
V
VOL
6,19
—
—
0.8
1.0
V
Output voltage
Output sink current
ISOURCE
6,19 FB = 1.6 V
—
–90
–45
µA
ISINK
6,19 FB = 1.6 V
1.5
6.0
—
mA
Duty cycle = 0 %
1.2
1.3
—
V
Duty cycle = Dtr
—
1.9
2.0
V
SEL = 0 V
85
90
95
%
SEL = 5 V
89
94
99
%
IO = –30 mA
CB –
1.4
CB –
1.1
—
V
IO = 30 mA
—
VS +
1.1
VS +
1.4
V
VTL
Threshold voltage
VTH
Maximum duty cycle
Output voltage
(Main side)
Output voltage
(Synchronous rectifier side)
Diode voltage
Control
block
Pin
No.
Threshold voltage
Output source current
General
Symbol
Dtr
8,11
14,17
8,11, CT = 500 pF
14,17 RT = 10 kΩ
VOH
8,17
VOL
8,17
VOH
11,14 IO = –30 mA
VB –
1.4
VB –
1.1
—
V
VOL
11,14 IO = 30 mA
—
0.1
0.5
V
VS = 16 V
CB = 22 V
VDIODE
13
IO = 10 mA
—
1.0
1.1
V
VIH
18
IC active mode
2.0
—
—
V
VIL
18
IC standby mode
—
—
1.0
V
Input current
ICTL
18
CTL = 5 V
—
50
80
µA
Standby current
ICCS
23
CTL = 0 V
—
—
10
µA
23
SEL = 0 V
(Normal mode)
—
5.2
7.8
mA
23
SEL = 5 V
(Low power mode)
—
1.0
1.5
mA
CTL input voltage
Power supply current
ICC
*: Standard design value.
7
MB3821
■ TYPICAL CHARACTERISTICS
10
Ta = +25 °C
SEL = 0 V
8
6
4
2
0
10
20
35
40
2.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
50
10
20
35
40
50
Power supply voltage VCC (V)
Power supply voltage VCC (V)
Reference voltage vs. power supply voltage
Reference voltage vs. power supply voltage
5
5
Ta = +25 °C
IOR = 0 mA
4
3
2
1
Ta = +25 °C
IOR = 0 mA
4
3
2
1
0
0
0
10
20
30
40
50
0
Power supply voltage VCC (V)
2
3
5
1.0
Reference voltage VREF (V)
VCC = 16 V
CTL = 5 V
IOR = 0 mA
1.5
0.5
0.0
−0.5
−1.0
−1.5
−20
0
20
40
60
80
Ambient temperature Ta (°C)
4
5
Reference voltage vs. control voltage
2.0
−2.0
−40
1
Power supply voltage VCC (V)
Reference voltage vs. ambient temperature
Reference voltage ∆VREF (%)
Ta = +25 °C
SEL = 5 V
1.8
Reference voltage VREF (V)
Reference voltage VREF (V)
0
Power supply current vs. power supply voltage
Power supply current ICC (mA)
Power supply current ICC (mA)
Power supply current vs. power supply voltage
100
Ta = +25 °C
VCC = 16 V
SEL = 0 V
IOR = 0 mA
4
3
2
1
0
0
10
20
30
40
50
Control voltage VCTL (V)
(Continued)
8
MB3821
(Continued)
Select pin current vs. select pin voltage
Control current vs. control voltage
500
Ta = +25 °C
VCC = 16 V
SEL = 0 V
400
Select pin current ISEL (µA)
Control current ICTL (µA)
500
300
200
100
0
0
10
20
30
40
1.5
Lower
1M
Triangular wave upper and lower
limit voltage VCT (V)
Triangular wave upper and lower
limit voltage VCT (V)
Upper
100 k
100
100 k
10 k
1k
10 p
100 p
1n
10 n
CT capacitance (F)
30
40
50
100 n
VCC = 16 V
CTL = 5 V
SEL = 0 V
2.4
2.2
2.0
Upper
1.8
RT = 10 kΩ, CT = 500 pF
1.6
1.4
1.2
Lower
1.0
0.8
0.6
−40
−20
0
20
40
60
80
100
Ambient temperature Ta (°C)
Triangular wave oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency fOSC (Hz)
VCC = 16 V
CTL = 5 V
SEL = 0 V
RT = 10 kΩ
1M
20
2.6
Triangular wave oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency
vs. CT capacitance
10 M
10
Select pin voltage VSEL (V)
Triangular wave upper and lower limit voltage
vs. ambient temperature
2.0
10 k
200
0
Ta = +25 °C
VCC = 16.0 V
CTL = 5 V
0.5
1k
300
0
Triangular wave upper and lower limit voltage
vs. triangular wave oscillator frequency
1.0
400
50
Control voltage VCTL (V)
2.5
Ta = +25 °C
VCC = 16 V
CTL = 5 V
Triangular wave oscillator frequency
vs. CT capacitance
1M
VCC = 16 V
CTL = 5 V
SEL = 5 V
RT = 10 kΩ
100 k
10 k
1k
100
10 p
100 p
1n
10 n
100 n
CT capacitance (F)
(Continued)
9
MB3821
(Continued)
Duty vs. oscillator frequency (ch1)
Duty vs. oscillator frequency (ch1)
100
100
Ta = +25 °C
VCC = 16 V
CTL = 5 V
SEL = 0 V
90
70
60
60
Duty Dtr (%)
70
50
40
30
40
30
20
10
10
100 k
Oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency
vs. timing resistance
10 M
Ta = +25 °C
VCC = 16 V
CTL = 5 V
SEL = 0 V
1M
CT = 100 pF
100 k
CT = 500 pF
10 k
CT = 15000 pF
1k
1k
10 k
100 k
Timing resistance RT (Ω)
Triangular wave oscillator frequency
vs. power supply voltage
250
Ta = +25 °C
CTL = 5 V
SEL = 0 V
240
230
220
210
RT = 10 kΩ, CT = 500 pF
200
190
180
170
160
150
0
10
20
0
100
1M
30
40
Power supply voltage VCC (V)
50
Triangular wave oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency fOSC (kHz)
50
20
0
10 k
10
80
1k
10 k
Oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency
vs. timing resistance
1M
Ta = +25 °C
VCC = 16 V
CTL = 5 V
SEL = 5 V
100 k
CT = 100 pF
10 k
CT = 500 pF
1k
CT = 15000 pF
100
1k
Triangular wave oscillator frequency fOSC (kHz)
Duty Dtr (%)
80
Ta = +25 °C
VCC = 16 V
CTL = 5 V
SEL = 5 V
90
10 k
100 k
Timing resistance RT (Ω)
Triangular wave oscillator frequency
vs. power supply voltage
25
Ta = +25 °C
CTL = 5 V
SEL = 5 V
24
23
22
RT = 10 kΩ, CT = 500 pF
21
20
19
18
17
16
15
0
10
20
30
40
Power supply voltage VCC (V)
50
MB3821
Triangular wave oscillator frequency
vs. ambient temperature
250
VCC = 16 V
CTL = 5 V
SEL = 0 V
240
230
220
210
RT = 10 kΩ, CT = 500 pF
200
190
180
170
160
150
−40
−20
0
20
40
60
80
100
Ambient temperature Ta (°C)
Triangular wave oscillator frequency fOSC (kHz)
Triangular wave oscillator frequency fOSC (kHz)
(Continued)
Triangular wave oscillator frequency
vs. ambient temperature
25
VCC = 16 V
CTL = 5 V
SEL = 5 V
24
23
22
21
RT = 10 kΩ, CT = 500 pF
20
19
18
17
16
15
−40
−20
0
20
40
60
80
100
Ambient temperature Ta (°C)
Error amplifier,gain and phase vs. frequency (ch1)
Ta = +25 °C
AV
90
φ
10
45
0
0
−10
−45
−20
−90
−30
−135
−40
−180
100
1k
10 k
100 k
1M
2.52 V
11 kΩ
1 µF
2.4 kΩ
240 kΩ
−
+
11 kΩ
Error amplifier
1.26 V
10 M
Frequency f (Hz)
Power dissipation vs. ambient temperature
Power dissipation PD (mW)
Gain AV (dB)
20
180
135
30
Phase φ (deg)
40
800
740
700
600
500
400
300
200
100
0
−40
−20
0
20
40
60
80
100
Ambient temperature Ta (°C)
11
MB3821
■ FUNCTIONAL DESCRIPTION
1. DC/DC Converter Function
(1) Reference voltage circuit (Ref)
The reference voltage circuit generates a temperature-compensated reference voltage (≅ 2.50 V) using the voltage
supplied from the power supply terminal (pin 23). This voltage is used as the reference voltage for the internal
circuits of the IC. The reference voltage can also be supplied to an external device from the VREF terminal (pin 24)
up to a maximum current of 1mA.
(2) Triangular-wave oscillator circuit (OSC)
By connecting a frequency setting capacitor and a resistor to the CT (pin 1) and the RT (pin 2) terminals, it is possible
to generate any desired triangular oscillation waveform.
The triangular wave is input to the PWM comparator within the IC.
(3) Error amplifier
This amplifier detects the output voltage of the DC/DC converter and outputs a PWM control signal accordingly.
The system can be provided with stable phase compensation by connecting a feedback resistor and capacitor
between the FB pin and the -IN pin of the error amplifier to create the desired level of loop gain.
Also, by connecting soft start capacitance to the CS terminal, which is the non inverted input pin for the error
amplifier, it is possible to prevent current surges when the power supply is started. By using the error amplifier for
soft start detection, it is possible to operate with a fixed soft start interval independent of the output load on the DC/
DC converter.
(4)
PWM comparators (PWM Comp.1, PWM Comp.2)
PWM Comp.1 and PWM Comp.2 are voltage-pulse width modulators that control the output duty according to input
voltage.
PWM Comp.1 controls the pulse width on the main side output circuit, and PWM Comp.2 controls the pulse width
on the synchronous rectifier side output circuit. The triangular wave generated by the triangular wave oscillator is
compared to the error amplifier output voltage, and in the intervals when the error amplifier voltage is higher than
the triangular wave, the main side output transistor is switched on and the synchronous rectifier side output transistor
is switched off.
Also, PWM Comp.1 is set to a maximum duty cycle of approximately 90 % (normal mode).
(5) Output circuit (Drive)
The output circuits is comprised of a totem-pole configuration on both the main side and synchronous rectifier side,
and can drive an external N-ch MOSFET.
(6) Mode select circuit (SEL)
The SEL terminal (pin 7) can set either channel to normal mode or low power mode.
In low power mode the triangular oscillator frequency is set to approximately 1/10 of normal mode, reducing the
internal power consumption of the chip and enabling high efficiency power supply at light load levels.
(7) Power supply control circuit (CTL)
The CTL terminal (pin 18) is used for power supply on/off control (standby power consumption is 10 µA or less).
2. Protection Functions
(1) Under Voltage Lockout Circuit (UVLO)
Power-on surge states or sudden drops in supply voltage can cause a control IC to operate abnormally, leading to
destruction or damage to system elements. The under voltage lockout circuit detects the internal reference voltage
level from the supply voltage, and shuts off the output transistors so that the inactive interval becomes 100%, holding
the CSCP terminal (pin 22) voltage at “L” level.
Operation is restored as soon as the supply voltage exceeds the under voltage lockout circuit threshold voltage.
12
MB3821
(2) Timer-Latch Short Circuit Protection Circuit (SCP)
This circuit detects the output voltage level from the error amplifier. When the error amplifier output voltage exceeds
approximately 2.1V, a timer circuit is activated and charges the external capacitor at the CSCP terminal (pin 22). If
the error amplifier output does not return to normal range before the capacitor voltage reaches approximately 0.7V,
a latch circuit is activated and sets both the main and synchronous rectifier side output pins to “L” level. After the
short protection circuit has been activated, it is reset by simply restarting the power supply. (See “METHOD OF
SETTING TIME CONSTANT FOR TIMER LATCH SHORT-CIRCUIT PROTECTION CIRCUIT”.)
13
MB3821
■ METHOD OF SETTING SOFT START TIME
To provide a soft start by preventing current surges at power-on, soft start capacitors (Cs1, Cs2) are connected to
both channels, the CS1 pin (pin 4) for CH1 and the CS2 pin (pin 21) for CH2.
When the IC is started (when the CTL pin (pin 18) goes to “H” level, and Vcc ≥ UVLO threshold voltage), transistors
Q2 and Q3 switch off and the CS1 and CS2 pins begin charging the external soft start capacitors (Cs1, Cs2) at 1 µA.
The error amplifier contributes to a soft start with the proportionate output voltage to the CS1 and CS2 pin voltage
regardless of the load current on the DC/DC converter.
The soft start time can be calculated by the following formula.
Soft start time (time to 100% output)
tS(sec) =: 1.26 × CS (µF)
Soft start circuit
1 µA
1 µA
FB1 6
−IN1 5
−
+
+
Error
Amp.1
Output stage
8
OUT1−1
4
CS1
1.26 V
Output stage
Cs1
Q2
11
OUT2−1
FB2 19
−IN2 20
−
+
+
Error
Amp.2
Output stage
OUT1−2
21
CS2
1.26 V
Cs2
Output stage
Q3
SCP Comp.
bias
22
S
CSCP
Q1
14
Q4
R
Latch
14
OUT2−2
−
−
+
1 µA
CSCP
17
2.1 V
bias
UVLO
Ref
(2.5V)
Power
ON/OFF
18
CTL
MB3821
■ TREATMENT WITHOUT USING CS TERMINAL
When you do not use the soft start circuit, open the CS1 terminal (pin 4) and CS2 terminal (pin 22).
Treatment When Not Using SCP
4 CS1
CS2 21
15
MB3821
■ METHOD OF SETTING TIME CONSTANT FOR TIMER-LATCH SHORT-CIRCUIT
PROTECTION CIRCUIT
The short detection comparator (SCP comparator) constantly compares the error amplifier output level to the
reference voltage.
While the switching regulator load conditions are stable on all channels, the short detection comparator output
remains at “H” level, transistor Q1 is on, and the CSCP terminal (pin 22) is held at input standby voltage (VSTB=: 50mV).
If the load conditions change rapidly due to a short-circuiting of load, causing the output voltage to drop, the output
from the short detection comparator goes to “L” level. This causes transistor Q1 to turn off and the external short
protection capacitor CSCP connected to the CSCP pin to charge at 1.0 µA.
Short Detection Time
tSCP(sec) =: 0.7 × CSCP (µF)
When the capacitor CSCP is charged to the threshold voltage VTH =: 0.7 V, the SR latch is set, and the external FET
is turned off (inactive interval is set to 100%). At this point, the SR latch input is closed and the CSCP terminal is
held at input latch voltage (VI =: 50 mV).
Timer-latch short-circuit protection circuit
1 µA
1 µA
FB1 6
−IN1 5
−
+
+
Error
Amp.1
Output stage
8
OUT1−1
4
CS1
1.26 V
Output stage
Cs1
Q2
11
OUT2−1
FB2 19
−IN2 20
−
+
+
Error
Amp.2
Output stage
CS2
1.26 V
Cs2
Output stage
Q3
SCP Comp.
bias
22
S
CSCP
Q1
16
Q4
R
Latch
14
OUT2−2
−
−
+
1 µA
CSCP
17
OUT1−2
21
2.1 V
bias
UVLO
Ref
(2.5V)
Power
ON/OFF
18
CTL
MB3821
■ TREATMENT WITHOUT USING CSCP TERMINAL
When you do not use the timer latch short-circuit protection circuit, connect the CSCP terminal (pin 22) to GND
with the shortest distance.
Treatment When Not Using SCP
3 GND
CSCP 22
■ Channel Control Method
On/off controls for either channel are enabled by setting the CS pins.
Setting Conditions
CS pin setting
Channel output state
CS1
CS2
CH1
CH2
GND
GND
OFF
OFF
GND
Open
OFF
ON
Open
GND
ON
OFF
Open
Open
ON
ON
17
MB3821
■ METHOD OF SETTING OSCILLATOR FREQUENCY
Oscillator Frequency can be set by timing capacitor (CT) connected to CT pin (pin 1) and timing resistor (RT)
connected to RT pin (pin 2).
Oscillator frequency
• Normal mode
fOSC (kHz) =:
1000000
CT(pF) × RT(kΩ)
• Low power mode
fOSC (kHz) =:
18
100000
CT(pF) × RT(kΩ)
0.1 µF
4
5
21
20
19
22
24
3
VREF GND
OFF : CTL= 0 V
10 kΩ
RT
ON : CTL= 5 V
2
Ref
Power
(2.5 V) ON/OFF
Low power mode : SEL= 5 V
500 pF
7
1
SEL CT
OSC
bias
1.3 V
1.9 V
Normal mode : SEL= 0 V
UVLO
Drive
Drive
Drive
Drive
Output ON/OFF signal
S
R
Latch
bias
2.1 V
−
PWM Comp.2
(40 mV)
+
−
PWM Comp.1
+
−
+
PWM Comp.2
(40 mV)
−
PWM Comp.1
+
OUT2−1
VS1
OUT1−1
VCC
CB1
+
100 µF −
Si9410
0.1 µF
100 µF Si9410
+
−
RB415D
OUT
6.8 µF
47 µH
+
−
IO 1
6.8 µF
+
−
IO 2
13 kΩ
21 kΩ
<3.3 V>
VO2
3.3 kΩ
9.8 kΩ
S-81250 : Seiko Instruments Inc.
2SK1299 : SANYO Electric Co., Ltd.
RB415D : ROHM Co., LTD
DE5SC3ML : SHINDENGEN ELECTRIC
MANUFACTURING Co., Ltd.
DE5SC3ML 150 µF
B
Si9410
47 µH
VO1
<5.0 V>
DE5SC3ML 150 µF
A
Si9410
100 µF +
−
0.1 µF
S-81250
Reg.
4.7 µF
IN
Si9410 : Siliconix Co.
GND (0)
OUT2−2
VS2
OUT1−2
CB2
18 CTL
12
14
16
17
15
RB415D
11
9
8
23
10
13
VB
10 µH
Mode select signal
−
−
+
1.26 V
Error Amp.
−
+
+
<< CH1>>
1.26 V
Error Amp.
−
+
+
1 µA
<< CH2>>
SCP Comp.
1 µA
1 µA
6
0.1 µF
CS2
−IN2
FB2
CSCP
2SK1299
10 kΩ
100 kΩ
10 kΩ
VXCS2
B
10 kΩ
0.022 µF
CS1
−IN1
FB1
0.1 µF
2SK1299
10 kΩ
100 kΩ
ON/OFF
Vin
10 kΩ
VXCS1
ON/OFF
0.022 µF
10 kΩ
A
Iin
MB3821
■ APPLICATION EXAMPLE
19
MB3821
■ REFERENCE DATA
• Load characteristic
Conversion efficiency vs. load current
Conversion efficiency vs. load current
5V output (3.3V output OFF)
3.3 V output (5 V output OFF)
100
Vin
16 kΩ
V
RT = 10
CT = 500 pF
VXCS1 = 5 V
VXCS2 = 0 V
95
90
RT = 10 kΩ
CT = 500 pF
VXCS1 = 5 V
VXCS2 = 0 V
95
Vin = 6 V
85
Vin = 16 V
80
75
70
Normal mode (SEL= 0V)
65
60
55
50
Low power mode (SEL= 5V)
45
Conversion efficiency (%)
Conversion efficiency (%)
100
40
90
85
Vin = 6 V
Vin = 16 V
80
75
Normal mode (SEL= 0V)
70
65
60
55
Low power mode (SEL= 5V)
50
45
40
0.001
0.005 0.01
0.05
0.1
0.5
1
5
10
0.001
0.005
0.01
0.05
0.1
0.5
1
5
10
Load current IO (A)
Load current IO (A)
• Normal mode
Conversion efficiency vs. Input voltage
Conversion efficiency vs. Input voltage
100
5 V output (3.3 V output OFF)
3.3 V output (5 V output OFF)
Conversion efficiency (%)
Conversion efficiency (%)
100
95
90
85
RT = 10 kΩ
CT = 500 pF
IO = 1 A
VXCS1 = 5 V
VXCS2 = 0 V
SEL = 0 V
80
75
70
5
6
7
8
9
10
11 12
13
Input voltage Vin (V)
14
15
16
95
90
85
RT = 10 kΩ
CT = 500 pF
IO = 1 A
VXCS1 = 0 V
VXCS2 = 5 V
SEL = 0 V
80
75
70
5
6
7
8
9
10
11 12
13
14
15
16
Input voltage Vin (V)
(Continued)
20
MB3821
(Continued))
• Low power mode
Conversion efficiency vs. Input voltage
Conversion efficiency vs. Input voltage
3.3 V output (5 V output OFF)
95
RT = 10 kΩ
CT = 500 pF
IO = 20 mA
VXCS1 = 5 V
VXCS2 = 0 V
SEL = 5 V
90
85
80
75
70
65
60
55
50
5
6
7
8
9
10
11 12
13
Input voltage Vin (V)
14
15
16
100
Conversion efficiency (%)
Conversion efficiency (%)
100
5 V output (3.3 V output OFF)
95
RT = 10 kΩ
CT = 500 pF
IO = 20 mA
VXCS1 = 0 V
VXCS2 = 5 V
SEL = 5 V
90
85
80
75
70
65
60
55
50
5
6
7
8
9
10
11 12
13
14
15
16
Input voltage Vin (V)
21
MB3821
■ USAGE PRECAUTIONS
1. Never use setting exceeding maximum rated conditions.
Exceeding maximum rated conditions may cause permanent damage to the LSI.
Also, it is recommended that recommended operating conditions be observed in normal use.
Exceeding recommended operating conditions may adversely affect LSI reliability.
2. Use this device within recommended operating conditions.
Recommended operating conditions are values within which normal LSI operation is warranted.
Standard electrical characteristics are warranted within the range of recommended operating conditions and
within the listed conditions for each parameter.
3. Printed circuit board ground lines should be set up with consideration for common
impedance.
4. Take appropriate static electricity measures.
•
•
•
•
Containers for semiconductor materials should have anti-static protection or be made of conductive material.
After mounting, printed circuit boards should be stored and shipped in conductive bags or containers.
Work platforms, tools, and instruments should be properly grounded.
Working personnel should be grounded with resistance of 250 kΩ to 1 MΩ between body and ground.
■ ORDERING INFORMATION
Part number
MB3821PFV
22
Package
24-pin plastic SSOP
(FPT-24P-M03)
Remarks
MB3821
■ PACKAGE DIMENSION
48-pin Plastic LQFP
(FPT-24P-M03)
*: These dimensions do not include resin protrusion.
+0.20
* 7.75±0.10(.305±.004)
1.25 –0.10
+.008
.049 –.004
(Mounting height)
0.10(.004)
* 5.60±0.10
INDEX
0.65±0.12(.0256±.0047)
(.220±.004)
+0.10
C
1994 FUJITSU LIMITED F24018S-2C-2
6.60(.260)
NOM
"A"
+0.05
0.22 –0.05
0.15 –0.02
+.004
–.002
.006 –.001
.009
7.15(.281)REF
7.60±0.20
(.299±.008)
Details of "A" part
+.002
0.10±0.10(.004±.004)
(STAND OFF)
0
10°
0.50±0.20
(.020±.008)
Dimensions in: mm (inches)
23
MB3821
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: 81(44) 754-3763
Fax: 81(44) 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/
F9905
 FUJITSU LIMITED Printed in Japan
24
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 are
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 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.