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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
s 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.
s 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
s PACKAGE
24-pin, Plastic SSOP
(FPT-24P-M03)
MB3821
s PIN ASSIGNMENT
(TOP VIEW)
CT : 1 RT : 2 GND : 3 CS1 : 4 IN -IN1 : 5 FB1 : 6
24 : VREF 23: VCC 22 : CSCP 21 : CS2 20 : -IN2 19 : FB2 18 : CTL 17 : OUT1-2 16 : VS2 15 : CB2 14: OUT2-2 13 :VB IN
(CH1)
SEL : 7 OUT1-1 : 8 VS1 : 9 CB1 : 10 OUT2-1 : 11 GND(0) : 12
(CH2)
OUT
OUT
(FPT-24P-M03)
2
MB3821
s PIN DESCRIPTION
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Symbol CT RT GND CS1 -IN1 FB1 SEL OUT1-1 VS1 CB1 OUT2-1 GND(0) VB OUT2-2 CB2 VS2 OUT1-2 CTL FB2 -IN2 CS2 CSCP VCC VREF I/O -- -- -- -- I O I I -- -- O -- -- O -- -- O I O I -- -- -- O Descriptions Triangular wave oscillator frequency setting capacitance connection pin. Triangular wave oscillator frequency setting resistance connection pin. Ground pin. Capacitor connection pin for Channel 1 soft start (also channel control). Channel 1 error amplifier inverted input pin. Channel 1 error amplifier output pin Mode select pin. Set the SEL pin to "H" level to switch the IC to low power mode. Totem pole type output pin (external main side FET gate drive). Channel 1 external main side FET source connection pin. Channel 1 boot capacitance connection pin. Channel 1 totem pole output pin (external main side FET gate drive). Ground pin for output circuit. Power supply pin for output circuit. Channel 2 totem pole output pin (external synchronous rectifier side FET gate drive). Channel 2 boot capacitance connection pin. Channel 2 external main side FET source connection pin. Channel 2 totem pole output pin (external main side FET gate drive). Power supply control pin. Set CTL pin to "L" to switch the IC to standby mode. Channel 2 error amplifier output pin. Channel 2 error amplifier inverted input pin. Channel 2 soft start capacitance connection pin(also channel control). Timer-latch short circuit protection capacitance connection pin. Reference power supply, control circuit power supply pin. Reference voltage output pin.
3
MB3821
s BLOCK DIAGRAM
1 1
13 VB
FB1 6 Error Amp. -IN1 5 - + + 1.26 V PWM Comp.2 (40 mV) + - Drive PWM Comp.1 + - Drive
10 CB1 23 VCC 8 OUT1-1 9 VS1
CS1 4
11 OUT2-1
< CH1 >
FB2 19 Error Amp. -IN2 20 - + + 1.26 V PWM Comp.2 (40 mV) + - Drive 14 OUT2-2 12 GND (0) - - + PWM Comp.1 + - Drive 17 OUT1-2 16 VS2 15 CB2
CS2 21
< CH2 >
SCP Comp. 1 CSCP 22 S R Latch UVLO OSC 1.9 V 2.1 V bias 1.3 V bias Ref Power (2.5 V) ON/OFF
18 CTL
7 SEL
1 CT
2 RT
24 VREF
3 GND
4
MB3821
s ABSOLUTE MAXIMUM RAGINGS
Parameter Power supply voltage Bias voltage Output current Output peak current Power dissipation Storage temperature Symbol VCC VB Io Io PD Tstg Conditions -- -- -- Duty 5 % Ta +25C -- Rating Min. -- -- -- -- -- -55 Max. 32 17 50 500 740* +125 Unit V V mA mA mW C
* : The packages are mounted on the epoxy board (10 cm x 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.
s RECOMMENDED OPERATING CONDITIONS
Parameter Power supply voltage Bias voltage Reference voltage output current Input voltage Output current Output peak current Timing capacitance Timing resistance Oscillator frequency Soft-start capacitance Short detection capacitance Boot capacitance Operating ambient temperature Symbol VCC VB IOR VIN IO Io CT RT fOSC CS CSCP CB Ta -IN pin SEL, CTL pin OUT pin Duty 5 % -- -- SEL = 0 V (Normal mode) SEL = 5 V (Low power mode) -- -- -- -- Conditions -- -- -- Value Min. 4.5 -- -1 0 0 -30 -300 150 6.8 10 1 -- -- -- -30 Typ. 16 6 -- -- -- -- -- 500 10 200 20 0.1 0.01 0.1 +25 Max. 30 16 0 VCC - 1.8 30 30 300 15000 12 500 50 1.0 1.0 1.0 +85 Unit V V mA V V mA mA pF k kHz kHz F F F 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.
5
MB3821
s ELECTRICAL CHARACTERISTICS
(VCC = 16 V, SEL =0 V, Ta = +25C) Parameter Output voltage Reference voltage block Output voltage temperature variation Input stability Load stability Short-circuit output current Under voltage lockout protection circuit block(U.V.L.O) Threshold voltage Hysteresis width Reset voltage Symbol VREF VREF /VREF Line Load IOS VTH VH VRST Pin No. 24 24 24 24 24 Conditions VREF =0 mA Ta = -30C to +85C VCC = 4.5 V to 30 V VREF = 0 mA to -1.0 mA VREF = 1 V Value Min. 2.45 -- -- -- -60 3.2 -- -- -- 2.4 Typ. 2.50 0.5* -- -- -25 3.5 0.18 2.8 Max. 2.55 -- 15 15 -- 3.8 -- -- Unit V % mV mV mA V V V A mV V A ms mV mV kHz kHz V V A % % % %
4,21 VCC = 4,21 4,21
Soft-start block
Charge current Input standby voltage Threshold voltage
ICS VSTB VTH ICSCP tSCP VSTB VI fOSC VLOW VHI ISEL f/fdv
4,21 4,21 4,21 22 22 22 22 8,11, CT = 500pF, 14,17 RT = 10 k 7 7 7 CSCP = 0.01 F
-- -- -- --
-1.4 -- 0.63 -1.4 4.5
-1.0 50 0.68 -1.0 6.8 50 50 200 20 -- -- 50 1 1 1* 1*
-0.6 100 0.73 -0.6 12.2 100 100 220 24 -- 1.0 80 10 10 -- --
Short circuit detection block
Input source current Short detection time Input standby voltage Input latch voltage Oscillator frequency Mode select voltage Input current Frequency stability for voltage Frequency stability for temperature
-- -- SEL = 0 V SEL = 5 V
-- -- 180 16 2.0 -- -- SEL = 0 V SEL = 5 V -- -- -- --
Low power mode Normal mode SEL = 5 V
Triangular wave oscillator block
CT = 500pF, 8,11, RT = 10 k 14,17 VCC = 4.5V to 30V
f/fdt
CT = 500pF, SEL = 0 V 8,11, RT = 10 k 14,17 Ta = -30C to +85C SEL = 5 V
*: Standard design value.
(Continued)
6
MB3821
(Continued)
(VCC = 16 V, SEL =0 V, Ta = +25C) Parameter Threshold voltage VT temperature stability Error amplifier block Input bias current Voltage gain Frequency bandwidth Output voltage Output source current Output sink current PWM Comp. block Threshold voltage VTH Symbol VTH VT /VT IB AV BW VOH VOL ISOURCE ISINK VTL Pin No. Conditions Value Min. 1.235 -- -200 60 -- -- -- VREF - 0.3 -- -- 1.5 1.2 -- 85 Typ. 1.260 0.5* -50 100 800* -- 0.8 -90 6.0 1.3 1.9 90 Max. 1.285 -- -- -- -- -- 1.0 -45 -- -- 2.0 95 Unit V % nA dB kHz V V A mA V V %
6,19 FB = 1.6 V 6,19 Ta = -30C to +85C 5,20 -IN = 0 V 6,19 DC 6,19 AV = 0 dB 6,19 6,19 6,19 FB = 1.6 V 6,19 FB = 1.6 V 8,11 14,17 Duty cycle = 0 % Duty cycle = Dtr SEL = 0 V
Dead time control block
Maximum duty cycle
Dtr
8,11, CT = 500 pF 14,17 RT = 10 k SEL = 5 V IO = -30 mA IO = 30 mA 89 CB - 1.4 -- VB - 1.4 -- -- 2.0 -- -- -- -- -- 94 CB - 1.1 VS + 1.1 VB - 1.1 0.1 1.0 -- -- 50 -- 5.2 1.0 99 %
Output block (Drive)
Output voltage (Main side)
VOH VOL VOH VOL VDIODE VIH VIL ICTL ICCS
8,17 8,17
VS = 16 V CB = 22 V
-- VS + 1.4 -- 0.5 1.1 -- 1.0 80 10 7.8 1.5
V V V V V V V A A mA mA
Output voltage (Synchronous rectifier side) Diode voltage
11,14 IO = -30 mA 11,14 IO = 30 mA 13 18 18 18 23 23 IO = 10 mA IC active mode IC standby mode CTL = 5 V CTL = 0 V SEL = 0 V (Normal mode) SEL = 5 V (Low power mode)
Control block General
CTL input voltage Input current Standby current
Power supply current
ICC 23
*: Standard design value.
7
MB3821
s TYPICAL CHARACTERISTICS
Power supply current vs. power supply voltage Power supply current ICC (mA)
10 8 6 4 2 0 0 10 20 35 40 50
Power supply current vs. power supply voltage Power supply current ICC (mA)
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 10 20 35 40 50 Ta = +25 C SEL = 5 V
Ta = +25 C SEL = 0 V
Power supply voltage VCC (V) Reference voltage vs. power supply voltage
5 Ta = +25 C IOR = 0 mA
Power supply voltage VCC (V) Reference voltage vs. power supply voltage
5
Reference voltage VREF (V)
4 3 2 1 0 0 10 20 30
Reference voltage VREF (V)
4 3 2 1 0
Ta = +25 C IOR = 0 mA
40
50
0
1
2
3
4
5
Power supply voltage VCC (V) Reference voltage vs. ambient temperature
2.0 5
Power supply voltage VCC (V) Reference voltage vs. control voltage
Ta = +25 C VCC = 16 V SEL = 0 V IOR = 0 mA
Reference voltage VREF (%)
1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0 -40 -20 0 20 40
Reference voltage VREF (V)
100
VCC = 16 V CTL = 5 V IOR = 0 mA
4 3 2 1 0 0 10 20 30
60
80
40
50
Ambient temperature Ta (C)
Control voltage VCTL (V)
(Continued)
8
MB3821
(Continued)
Control current vs. control voltage
500
Select pin current vs. select pin voltage
500
400 300 200 100 0 0 10 20 30
Select pin current ISEL (A)
Control current ICTL (A)
Ta = +25 C VCC = 16 V SEL = 0 V
400 300 200 100 0 0 10 20 30
Ta = +25 C VCC = 16 V CTL = 5 V
40
50
40
50
Control voltage VCTL (V) Triangular wave upper and lower limit voltage vs. triangular wave oscillator frequency Triangular wave upper and lower limit voltage VCT (V) Triangular wave upper and lower limit voltage VCT (V)
2.5 Ta = +25 C VCC = 16.0 V CTL = 5 V
Select pin voltage VSEL (V) Triangular wave upper and lower limit voltage vs. ambient temperature
2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 -40 -20 0 20 40 60 80 100 VCC = 16 V CTL = 5 V SEL = 0 V
2.0
Upper
1.5
Upper
RT = 10 k, CT = 500 pF
1.0
Lower
Lower
0.5 1k
10 k
100 k
1M
Triangular wave oscillator frequency fOSC (Hz) Triangular wave oscillator frequency vs. CT capacitance Triangular wave oscillator frequency fOSC (Hz)
10 M
Ambient temperature Ta (C) Triangular wave oscillator frequency fOSC (Hz) Triangular wave oscillator frequency vs. CT capacitance
1M VCC = 16 V CTL = 5 V SEL = 5 V RT = 10 k
1M
VCC = 16 V CTL = 5 V SEL = 0 V RT = 10 k
100 k
100 k
10 k
10 k
1k
1k 10 p
100 p
1n
10 n
100 n
100 10 p
100 p
1n
10 n
100 n
CT capacitance (F)
CT capacitance (F)
(Continued)
9
MB3821
(Continued)
Duty vs. oscillator frequency (ch1)
100 90 80 70
Duty vs. oscillator frequency (ch1)
100 90 80 70 Ta = +25 C VCC = 16 V CTL = 5 V SEL = 5 V
Ta = +25 C VCC = 16 V CTL = 5 V SEL = 0 V
Duty Dtr (%)
Duty Dtr (%)
60 50 40 30 20 10 0 10 k 100 k 1M
60 50 40 30 20 10 0 100 1k 10 k
Triangular wave oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency fOSC (Hz)
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
Oscillator frequency fOSC (Hz) Triangular wave oscillator frequency vs. timing resistance
1M Ta = +25 C VCC = 16 V CTL = 5 V SEL = 5 V
1M
100 k
CT = 100 pF 100 k CT = 500 pF
CT = 100 pF 10 k CT = 500 pF
10 k CT = 15000 pF 1k 1k 10 k 100 k
1k CT = 15000 pF 100 1k 10 k 100 k
Triangular wave oscillator frequency fOSC (kHz)
Timing resistance RT () Triangular wave oscillator frequency vs. power supply voltage
250 240 230 220 210 200 190 180 170 160 150 0 10 20 30 40 50 RT = 10 k, CT = 500 pF Ta = +25 C CTL = 5 V SEL = 0 V
Triangular wave oscillator frequency fOSC (kHz)
Timing resistance RT () Triangular wave oscillator frequency vs. power supply voltage
25 24 23 22 21 20 19 18 17 16 15 0 10 20 30 40 50 Ta = +25 C CTL = 5 V SEL = 5 V RT = 10 k, CT = 500 pF
Power supply voltage VCC (V)
Power supply voltage VCC (V)
10
MB3821
(Continued)
Triangular wave oscillator frequency fOSC (kHz) Triangular wave oscillator frequency fOSC (kHz) Triangular wave oscillator frequency vs. ambient temperature
250 240 230 220 210 200 190 180 170 160 150 -40 -20 0 20 40 60 80 100 RT = 10 k, CT = 500 pF VCC = 16 V CTL = 5 V SEL = 0 V
Triangular wave oscillator frequency vs. ambient temperature
25 24 23 22 21 20 19 18 17 16 15 -40 -20 0 20 40 60 80 100 RT = 10 k, CT = 500 pF VCC = 16 V CTL = 5 V SEL = 5 V
Ambient temperature Ta (C) Error amplifier,gain and phase vs. frequency (ch1)
40 30 20 10 0 -10 -20 -30 -40 100 1k 10 k 100 k 1M Ta = +25 C AV 180 135 45 0 -45 -90 -135 -180 10 M 90
Ambient temperature Ta (C)
Phase (deg)
Gain AV (dB)
2.52 V 11 k 1 F 2.4 k 240 k - + 11 k 1.26 V
Error amplifier
Frequency f (Hz) Power dissipation vs. ambient temperature Power dissipation PD (mW)
800 740 700 600 500 400 300 200 100 0 -40 -20 0 20 40 60 80 100
Ambient temperature Ta (C)
11
MB3821
s 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 A 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
s 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 A. 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 x CS (F)
Soft start circuit
1 A 1 A
FB1 6 -IN1 5 - + + 1.26 V Error Amp.1
Output stage
8 OUT1-1
4 CS1 Cs1 Q2
Output stage
11 OUT2-1
FB2 19 -IN2 20 - + + 1.26 V Error Amp.2
Output stage
17 OUT1-2
21 CS2 Cs2 Q3 SCP Comp. - - + bias R Latch 2.1 V bias Ref (2.5V) Power ON/OFF
Output stage
14 OUT2-2
1 A CSCP 22 S Q1 Q4
CSCP
UVLO
18 CTL
14
MB3821
s 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
s 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 A. Short Detection Time : tSCP(sec) = 0.7 x CSCP (F) : 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 A 1 A
FB1 6 -IN1 5 - + + 1.26 V Error Amp.1
Output stage
8 OUT1-1
4 CS1 Cs1 Q2
Output stage
11 OUT2-1
FB2 19 -IN2 20 - + + 1.26 V Error Amp.2
Output stage
17 OUT1-2
21 CS2 Cs2 Q3 SCP Comp. - - + bias 2.1 V bias Ref (2.5V) Power ON/OFF
Output stage
14 OUT2-2
1 A CSCP 22 S Q1 Q4
CSCP
R Latch
UVLO
18 CTL
16
MB3821
s 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
s Channel Control Method
On/off controls for either channel are enabled by setting the CS pins. Setting Conditions CS pin setting CS1 GND GND Open Open CS2 GND Open GND Open Channel output state CH1 OFF OFF ON ON CH2 OFF ON OFF ON
17
MB3821
s 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) x RT(k)
* Low power mode
: fOSC (kHz) = 100000 CT(pF) x RT(k)
18
Iin 10 H 4.7 F 1 A 13 RB415D 10 23 Drive Si9410 VS1 9 OUT2-1 8 OUT1-1 6.8 F VCC 47 H Error Amp. - + + PWM Comp.1 + - PWM Comp.2 (40 mV) + - Drive RB415D 15 PWM Comp.1 + - 16 VS2 Drive 17 OUT1-2 Error Amp. - + + + 100 F - Si9410 6.8 F + - 1.26 V PWM Comp.2 (40 mV) + - Drive << CH2>> SCP Comp. - - + 1.9 V 2.1 V bias S R Latch UVLO OSC 2 RT 10 k 7 1 SEL CT 500 pF 1.3 V bias Ref Power (2.5 V) ON/OFF 24 3 VREF GND 18 CTL 14 12 CB2 0.1 F Si9410 47 H 11 << CH1>> 100 F Si9410 + - + - 1.26 V CB1 IO1 VO1 <5.0 V> 9.8 k 3.3 k 100 F + - 0.1 F VB
IN
S-81250 Reg. OUT
1 A
FB1
6
ON/OFF
0.022 F 10 k A
-IN1
5
s APPLICATION EXAMPLE
VXCS1
10 k
CS1
4
10 k
0.1 F
2SK1299
DE5SC3ML 150 F A IO2 VO2 <3.3 V> 21 k 13 k
Vin
100 k
FB2
0.022 F
19
10 k
ON/OFF
B
-IN2
20
VXCS2
CS2
10 k
21
10 k
0.1 F
OUT2-2 GND (0)
2SK1299
DE5SC3ML 150 F B
100 k
1 A
CSCP
22
0.1 F
Si9410 : Siliconix Co. Output ON/OFF signal ON : CTL= 5 V OFF : CTL= 0 V DE5SC3ML : SHINDENGEN ELECTRIC MANUFACTURING Co., Ltd. RB415D : ROHM Co., LTD 2SK1299 : SANYO Electric Co., Ltd. S-81250 : Seiko Instruments Inc.
Mode select signal Normal mode : SEL= 0 V Low power mode : SEL= 5 V
MB3821
19
MB3821
s REFERENCE DATA
* Load characteristic
Conversion efficiency vs. load current
3.3 V output (5 V output OFF)
100
Conversion efficiency vs. load current
5V output (3.3V output OFF)
100 95 RT = 10 k CT = 500 pF VXCS1 = 5 V VXCS2 = 0 V
Conversion efficiency (%)
95 90 85 80 75 70 65 60 55 50 45 40 0.001
Vin = 6 V
Conversion efficiency (%)
Vin = 10 k RT 16 V CT = 500 pF VXCS1 = 5 V VXCS2 = 0 V
Vin = 6 V Vin = 16 V
90 85 80 75 70 65 60 55 50 45 40
Vin = 16 V
Normal mode (SEL= 0V)
Normal mode (SEL= 0V)
Low power mode (SEL= 5V)
Low power mode (SEL= 5V)
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
100
Conversion efficiency (%)
Conversion efficiency (%)
3.3 V output (5 V output OFF)
5 V output (3.3 V output OFF)
95 90 85 80 75 70
95 90 85 80 75 70
RT = 10 k CT = 500 pF IO = 1 A VXCS1 = 5 V VXCS2 = 0 V SEL = 0 V 5 6 7 8 9 10 11 12 13 14 15 16
RT = 10 k CT = 500 pF IO = 1 A VXCS1 = 0 V VXCS2 = 5 V SEL = 0 V 5 6 7 8 9 10 11 12 13 14 15 16
Input voltage Vin (V)
Input voltage Vin (V)
(Continued)
20
MB3821
(Continued))
* Low power mode
Conversion efficiency vs. Input voltage
100 100
Conversion efficiency vs. Input voltage
Conversion efficiency (%)
95 90 85 80 75 70 65 60 55 50 5 6 7 8 9 10 11 12
Conversion efficiency (%)
3.3 V output (5 V output OFF)
RT = 10 k CT = 500 pF IO = 20 mA VXCS1 = 5 V VXCS2 = 0 V SEL = 5 V
95 90 85 80 75 70 65 60 55 50 5 6 7 8
5 V output (3.3 V output OFF)
RT = 10 k CT = 500 pF IO = 20 mA VXCS1 = 0 V VXCS2 = 5 V SEL = 5 V
13
14
15
16
9
10
11 12
13
14
15
16
Input voltage Vin (V)
Input voltage Vin (V)
21
MB3821
s 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 k to 1 M between body and ground.
s ORDERING INFORMATION
Part number MB3821PFV Package 24-pin plastic SSOP (FPT-24P-M03) Remarks
22
MB3821
s PACKAGE DIMENSION
48-pin Plastic LQFP (FPT-24P-M03)
*: These dimensions do not include resin protrusion.
* 7.750.10(.305.004)
1.25 -0.10 .049 -.004
+0.20 +.008
(Mounting height)
0.10(.004)
* 5.600.10
INDEX (.220.004)
7.600.20 (.299.008)
6.60(.260) NOM
0.650.12(.0256.0047)
0.22 -0.05 .009
+0.10 +.004 -.002
"A"
0.15 -0.02 .006 -.001
+0.05 +.002
Details of "A" part 0.100.10(.004.004) (STAND OFF)
7.15(.281)REF
0
10
0.500.20 (.020.008)
C
1994 FUJITSU LIMITED F24018S-2C-2
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
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.
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 (c) FUJITSU LIMITED Printed in Japan
24

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