FUJITSU MB3828

FUJITSU SEMICONDUCTOR
DATA SHEET
DS04-27217-5E
ASSP For Power Supply Applications
Pentium® DC/DC Converter IC
MB3828
■ DESCRIPTION
The FUJITSU MB3828 is a pulse width modulation (PWM) DC/DC converter IC chip that provides a selection of
1.3 V to 3.5 V output voltages for Pentium®* CPU’s, using a 5-bit input signal information.
The MB3828 utilizes synchronous rectification for high efficiency and features a soft-start/discharge control
function for ease in designing power supplies in multi-supply systems, making it ideal for Pentium® power supply
systems.
* : Pentium is the registered trademark of Intel Corporation.
■ FEATURES
•
•
•
•
•
•
•
•
Highly efficient for using synchronous rectification scheme
On-chip soft-start/discharge control circuit
High precision output voltage: ±1.2%
5-bit, 32-step DAC: 3.5 V to 2.1 V in 100 mV steps
2.05 V to 1.3 V in 50 mV steps
Frequency range: 100 kHz to 500 kHz using variable resistance (on-chip frequency setting capacitance)
Standby current: 0 µA TYP
On-chip PWRGOOD circuit for output voltage state detection
Timer-latch short-circuit protection circuit, and overvoltage protection circuit for output protection
■ PACKAGE
24-pin Plastic SSOP
(FPT-24P-M03)
MB3828
■ PIN ASSIGNMENT
(Top view)
RT : 1
24 : VREF
RS : 2
23 : VCC
SGND : 3
22 : CSCP
CS : 4
21 : PWRGOOD
–IN : 5
20 : VSENSE
FB : 6
19 : CTL
ENB : 7
18 : VD4
OUT1 : 8
17 : VD3
VS : 9
16 : VD2
CB : 10
15 : VD1
OUT2 : 11
14 : VD0
PGND : 12
13 : VB
(FPT-24P-M03)
2
MB3828
■ PIN DESCRIPTION
Pin no.
Symbol
I/O
Descriptions
1
RT
—
Triangular wave frequency setting resistor connection pin
2
RS
—
Discharging resistor connection pin for soft start capacitor
3
SGND
—
Ground pin
4
CS
—
Soft start capacitor connection pin (Also used for discharge control)
5
–IN
I
Error amplifier inverted input pin
6
FB
O
Error amplifier output pin
7
ENB
I
Discharge control function enable/disable switch control pin
8
OUT1
O
Totem-pole output pin (External main-side FET gate drive)
9
VS
—
External main-side FET source-side connection
10
CB
—
Output bootstrap pin
Insert a capacitor between the CB and VS pins, to bootstrap the IC internal
output transistor.
11
OUT2
O
Totem-pole output pin (External synchronous rectifier-side FET gate drive)
12
PGND
—
Ground pin
13
VB
—
Output circuit power supply pin
14
VD0
I
5-bit digital input pin used to set DC/DC converter output voltage
15
VD1
I
5-bit digital input pin used to set DC/DC converter output voltage
16
VD2
I
5-bit digital input pin used to set DC/DC converter output voltage
17
VD3
I
5-bit digital input pin used to set DC/DC converter output voltage
18
VD4
I
5-bit digital input pin used to set DC/DC converter output voltage
19
CTL
I
Power supply control pin
The CTL pin is set to “L” level to place the IC in standby mode.
20
VSENSE
I
PWRGOOD circuit input pin
21
PWRGOOD
O
PWRGOOD output pin (open-drain output)
Outputs a “H” level signal when the output voltage is within the range from
VTLOW to VTHIGH.
22
CSCP
—
Timer-latch short-circuit protection capacitor connection pin
23
VCC
—
Power supply pin for reference power and control circuit
24
VREF
O
Reference voltage output pin
3
MB3828
■ BLOCK DIAGRAM
VSENSE
PWRGOOD
21
20
POWERGOOD
PWRGD
CS
–IN
FB
–
+
+
5
(±10%)
13
Overvoltage
protection
(17.5%)
OVP
PWM
Comp.1
+
+
DTC
–
Error
Amp.
10
Drive
1
6
PWM
Comp.2
VB
RS
VB
CB
OUT1
8
9
VS
+
2
–
CS
Drive
2
4
OUT2
11
12
PGND
+
VD0 14
VD1 15
VD2 16
VCS
D/A
CS
Comp.
bias
19 CTL
7 ENB
(5-bit)
SCP
Comp.
VD3 17
bias
+
VD4 18
OSC
SCP
VSCP
CT
(40 pF)
1
RT
4
CTL
LOGIC
–
–
UVLO
Ref
Power
ON/OFF
CTL
(3.5 V)
22
CSCP
24
3
VREF SGND
VCC
23
MB3828
■ OUTPUT VOLTAGE SETTING CODE
VD4
VD3
VD2
VD1
VD0
VD (DC/DC converter output voltage)
(V)
1
0
0
0
0
3.500
1
0
0
0
1
3.400
1
0
0
1
0
3.300
1
0
0
1
1
3.200
1
0
1
0
0
3.100
1
0
1
0
1
3.000
1
0
1
1
0
2.900
1
0
1
1
1
2.800
1
1
0
0
0
2.700
1
1
0
0
1
2.600
1
1
0
1
0
2.500
1
1
0
1
1
2.400
1
1
1
0
0
2.300
1
1
1
0
1
2.200
1
1
1
1
0
2.100
1
1
1
1
1
0 (output OFF)
0
0
0
0
0
2.050
0
0
0
0
1
2.000
0
0
0
1
0
1.950
0
0
0
1
1
1.900
0
0
1
0
0
1.850
0
0
1
0
1
1.800
0
0
1
1
0
1.750
0
0
1
1
1
1.700
0
1
0
0
0
1.650
0
1
0
0
1
1.600
0
1
0
1
0
1.550
0
1
0
1
1
1.500
0
1
1
0
0
1.450
0
1
1
0
1
1.400
0
1
1
1
0
1.350
0
1
1
1
1
1.300
5
MB3828
■ ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol
Condition
Value
Unit
Power supply voltage
VCC
—
20
V
Bias voltage
VB
—
20
V
Boot voltage
VCB
—
32
V
Control input voltage
VCTL
—
20
V
PWRGOOD output voltage
VPWRGD
—
17
V
Output current
IO
—
50
mA
Peak output current
IO
Duty ≤ 5% (t = 1/fOSC × Duty)
500
mA
Allowable dissipation
PD
Ta ≤ +25°C
740*
mW
Storage temperature
Tstg
–55 to +125
°C
—
* : When mounted on a 10 cm-square dual-sided epoxy base board
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.
6
MB3828
■ RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Condition
Value
Min.
Typ.
Max.
Unit
Power supply voltage
VCC
—
4.6
5
18
V
Bias voltage
VB
—
—
5
18
V
Boot voltage
VCB
—
—
—
30
V
Reference voltage output
current
IOR
—
–1
—
0
mA
VIN
–IN pin
0
—
VCC – 0.9
V
VIN
CTL, ENB, VD4 to
VD0 pins
0
—
18
V
VIN
VSENSE
0
—
VCC
V
IO
OUT pin
–30
—
30
mA
IPG
PWRGOOD pin
—
—
1
mA
Peak output current
IO
Duty ≤ 5%
(t = 1/fOSC × Duty)
–300
—
300
mA
Oscillator frequency
fOSC
—
100
200
500
kHz
Timing resistance
RT
—
51
130
270
kΩ
Boot capacitance
CB
—
—
0.1
1.0
µF
Reference voltage output
capacitance
CREF
—
—
0.1
1.0
µF
Soft start capacitance
CS
—
—
4700
10000
pF
Discharge control resistance
RS
—
—
100
470
kΩ
Short detection capacitance
CSCP
—
—
2200
10000
pF
Operating temperature
Ta
—
–30
+25
+85
°C
Input voltage
Output current
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 the recommended operating conditions. 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 representative beforehand.
7
MB3828
■ ELECTRICAL CHARACTERISTICS
(Ta = +25°C, VCC = 5 V)
Parameter
Reference
voltage block
(Ref)
Under voltage
lockout circuit
block (UVLO)
Soft start block
(CS)
Symbol
Min.
Typ.
Max.
Unit
24
VREF = 0 mA
Output voltage
temperature
regulation
∆VREF
/VREF
24
Ta = –30°C to +85°C*
—
0.5
—
%
Input stability
Line
24
VCC = 4.6 V to 18 V
—
1
10
mV
Load stability
Load
24
IO = 0 mA to –1 mA
—
3
10
mV
Short circuit output
current
IOS
24
VREF = 1 V
–20
–10
–3
mA
Threshold voltage
VTH
4
VCC =
3.4
3.7
4.0
V
Hysteresis voltage
VH
4
—
—
0.18
0.21
V
Reset voltage
VRST
4
—
1.7
2.1
—
V
Charge current
ICS
4
—
–2.8
–2.0
–1.2
µA
4
—
0.63
0.68
0.73
V
22
—
–2.8
–2.0
–1.2
µA
0.50
0.75
1.34
ms
180
200
220
kHz
—
1
—
%
22
CSCP = 2200 pF
Oscillator frequency fOSC
8, 11 RT = 130 kΩ
Frequency
temperature
regulation
8, 11 Ta = –30°C to +85°C*
∆f/fdt
3.465 3.500 3.535
V
VTH1
6
FB = 1.6 V,
VD4 to VD0 = 00101
1.7784
1.8000
1.8216
V
VTH2
6
FB = 1.6 V,
VD4 to VD0 = 11010
2.4700
2.5000
2.5300
V
VTH temperature
regulation
∆VT/VT
6
Ta = –30°C to +85°C*
—
0.5
—
%
Input bias current
IB
5
–IN = 0 V
–200
–50
—
nA
Voltage gain
AV
6
DC
60
100
—
dB
Frequency
bandwidth
BW
6
AV = 0 dB*
—
800
—
kHz
VOH
6
—
2.18
3.5
—
V
VOL
6
—
—
0.8
1.0
V
Output source
current
ISOURCE
6
FB = 1.6 V
—
–90
–45
µA
Output sink current
ISINK
6
FB = 1.6 V
3.0
12.0
—
mA
Output voltage
* : Standard design value
8
Value
VREF
Threshold voltage
Error amplifier
block (Error
Amp.)
Condition
Output voltage
Threshold voltage
VTH
Short circuit
Input source current ICSCP
protection
comparator block
Short detection
(SCP)
tSCP
interval
Triangular wave
oscillator block
(OSC)
Pin
no.
(Continued)
MB3828
(Ta = +25°C, VCC = 5 V)
Parameter
PWM comparator
blocks (PWM
Threshold voltage
Comp.1, 2)
Symbol
Pin
no.
Condition
Typ.
Max.
Unit
8, 11 Duty cycle = 0%
1.2
1.3
—
V
VTH
8, 11 Duty cycle = Dtr
—
1.86
2.0
V
85
90
95
%
—
V
8
RT = 130 kΩ
VOH
8
OUT1 = –30 mA,
VB = 5 V, CB = 20 V,
VS = 15 V
VOL
8
OUT1 = 30 mA,
VB = 5 V, CB = 22 V,
VS = 15 V
Output voltage
(main side)
Output blocks
(Drive1, 2)
CB – 1.4 CB – 1.1
—
VS + 1.1
VS + 1.4
V
VB – 1.4
VB – 1.1
—
V
Output voltage
(synchronized
rectifier side)
VOH
11
OUT2 = –30 mA,
VB = 5 V
VOL
11
OUT2 = 30 mA,
VB = 5 V
—
0.1
0.5
V
Diode voltage
VDIODE
13
IDIODE = 10 mA
—
1.0
1.1
V
VIH
24
IC operating mode
2.0
—
18
V
VIL
24
IC standby mode
0
—
1.0
V
ICTL
19
CTL = 5 V
—
100
160
µA
VTLOW
21
VD4 to VD0 setting,
VSENSE =
0.88
× VD
0.90
× VD
0.92
× VD
V
VTHIGH
21
VD4 to VD0 setting,
VSENSE =
1.08
× VD
1.10
× VD
1.12
× VD
V
Hysteresis voltage
VH
21
3
30
50
mV
Output leak current
ILEAK
21
PWRGOOD = 5 V
—
—
40
µA
Output voltage
VOL
21
PWRGOOD = 1 mA
—
0.06
0.4
V
VTH
24
CS =
—
0.05
0.07
V
VIH
24
Discharge control ON
2.0
—
18
V
VIL
24
Discharge control
OFF
0
—
1.0
V
IENB
7
ENB = 0 V
–1.0
–0.05
—
µA
CTL input voltage
Input current
PWRGOOD
comparator
protection block
(PWRGD)
Min.
VTL
Dead time control
Maximum duty cycle Dtr
block (DTC)
Control block
(CTL)
Value
Threshold voltage
Discharge control
comparator (CS Threshold voltage
Comp.)
Discharge control ENB input voltage
ON/OFF block
(CTL LOGIC)
Input current
—
(Continued)
9
MB3828
(Continued)
(Ta = +25°C, VCC = 5 V)
Parameter
Threshold voltage
Over voltage
protection
comparator block Hysteresis voltage
(OVP)
VSENSE pin input
current
Pin
no.
Condition
VTH
8, 11 VSENSE =
VD = 1.3 V
VH
8, 11
ISENSE
20
,
—
VSENSE = 0 V
Value
Min.
1.15
× VD
Typ.
Max.
1.175 1.20
× VD × VD
Unit
V
3
30
50
mV
–10
–0.1
—
µA
D/A input voltage
VIH
14 to
18
—
2.0
—
18
V
D/A (VD4 to VD0
D/A input voltage
pin) (D/A)
VIL
14 to
18
—
0
—
1.0
V
Input current
ID
14 to
18
VD4 to VD0 = 5 V
—
0.05
1.0
µA
Standby current
ICCS
23
CTL = 0 V
—
0
10
µA
Power supply
current
ICC
23
—
4.0
6.0
mA
General
10
Symbol
—
MB3828
■ TYPICAL CHARACTERISTICS
5.0
Reference voltage vs. Power supply voltage characteristics
5.0
Ta = +25°C
VB = 5 V
Reference voltage VREF (V)
Power supply current ICC (mA)
Power supply current vs.
Power supply voltage characteristics
4.0
3.0
2.0
1.0
0
4.0
3.0
2.0
1.0
0
0
5.0
10.0
15.0
20.0
25.0
0
4.0
8.0
12.0
16.0
20.0
Power supply voltage VCC (V)
Power supply voltage VCC (V)
VREF vs. Temperature characteristics
Reference voltage, CTL pin current vs. Control voltage
3.55
3.50
3.45
3.40
–40.0 –20.0
5.0
0.0
20.0
40.0
60.0
Ta = +25°C
VB = 5 V
VREF
4.0
500.0
400.0
3.0
300.0
ICTL
2.0
200.0
1.0
100.0
Control pin current ICTL (µA)
VCC = 16 V, VB = 5 V, RT = 130 kΩ
Reference voltage VREF (V)
Reference voltage VREF (V)
3.60
80.0 100.0
Temperature Ta (°C)
0
0
5.0
10.0
15.0
20.0
0
25.0
Control voltage VCTL (V)
3.60
VCC = 16 V, VB = 5 V, RT = 130 kΩ
3.55
3.50
3.45
3.40
–40.0 –20.0
0.0
20.0
40.0
60.0 80.0 100.0
Temperature Ta (°C)
ERR threshold (2.0 V setting) vs.
Temperature characteristics
ERR threshold (2.0 V setting) (V)
ERR threshold (3.5 V setting) (V)
ERR threshold (3.5 V setting) vs.
Temperature characteristics
2.04
VCC = 16 V, VB = 5 V, RT = 130 kΩ
2.02
2.00
1.98
196
1.94
–40.0 –20.0
0.0
20.0
40.0
60.0
80.0 100.0
Temperature Ta (°C)
(Continued)
11
MB3828
ERR threshold (1.3 V setting) (V)
ERR threshold (1.3 V setting) vs. Temperature characteristics
1.34
VCC = 16 V, VB = 5 V, RT = 130 kΩ
1.32
1.30
1.28
1.26
1.24
–40.0 –20.0
0.0
20.0
40.0
60.0
80.0 100.0
Temperature Ta (°C)
Error Amp. gain, Phase vs. Frequency characteristics
Error Amp.
40
30
φ
Gain AV (dB)
20
10
180
90
45
AV
0
3V
135
0
–10
–45
–20
–90
–30
–135
–40
–180
1K
10 K
100 K
1M
240 kΩ
10 kΩ
Phase φ (°)
Ta = +25°C
VCC = 16 V
VB = 5 V
IN
1 µF
2.4 kΩ
VREF
–
+
+
OUT
10 kΩ
1.5 V
10 M
Frequency f (HZ)
(Continued)
12
MB3828
(Continued)
Triangular wave oscillator frequency vs.
Timing resistance characteristics
Oscillator Frequency fosc (kHz)
220
VB = 5 V, RT = 130 kΩ
210
200
190
180
1000
VCC = 16 V, VB = 5 V
100
10
10
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
100
1000
Timing resistance RT (kΩ)
Power supply voltage VCC (V)
Triangular wave oscillator frequency vs. Temperature characteristics
Oscillator frequency fosc (kHz)
Oscillator frequency fosc (kHz)
Triangular wave oscillator frequency vs.
Power supply voltage characteristics
220
VCC = 16 V, VB = 5 V, RT = 130 kΩ
210
200
190
180
–40.0 –20.0
0.0
20.0
40.0
60.0
80.0 100.0
Temperature Ta (°C)
13
MB3828
■ FUNCTION DESCRIPTION
1. Switching Regulator Function
(1) Reference voltage circuit (Ref)
The reference voltage circuit uses the voltage supply from the VCC pin (pin 23) to generate a temperature
compensated reference voltage (≅ 3.5 V) for use as the reference voltage for the internal circuits of the IC chip.
It is also possible to supply a reference voltage output of up to 1 mA to external circuits through the VREF pin
(pin 24).
(2) Triangular wave oscillator (OSC)
The triangular wave form is generated using an on-chip frequency selection capacitor, plus the frequency
selection resistance connected to the RT pin (pin 1).
The triangular wave is input to the PWM comparator circuits on the IC.
(3) Error amplifier (Error Amp.)
The error amplifier circuit is used to detect the output voltage from the DC/DC converter for output as the PWM
control signal. The in-phase input range covers the full range from 0 V to VCC – 0.9 V. By connecting a feedback
resistance and capacitor between the FB pin (pin 6) and –IN pin (pin 5), it is possible to create any desired
level of loop gain, thereby providing stable phase compensation to the system.
Also, it is possible to prevent current spikes at power supply start-up by connecting a soft start capacitor to the
CS pin (pin 4), the non-inverting input pin for Error Amp. The use of Error Amp. for soft start detection makes
it possible for a system to operate on a fixed soft start time that is 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 converters that control output voltage 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 with the output voltage from Error
Amp., and during intervals when Error Amp. output is higher than the triangular wave, the main-side output
transistor is switched on and the synchronous rectifier side output transistor is turned off.
PWM Comp.1 is set to a maximum duty cycle of approximately 90%.
(5) Output circuits (Drive1, Drive2)
The output circuits on both the main-side and synchronous rectifier-side have a totem-pole configuration, and
are capable of driving an external N-ch. MOS FET.
(6) Power supply control circuit (CTL)
This circuit is able to control power supply ON/OFF switching from the CTL pin (pin 19). (During standby mode,
supply current is 0 µA TYP.)
(7) DAC circuit (D/A)
This circuit controls the output voltage to the CPU between 1.3 V and 3.5 V, as selected by the 5-bit (32-step)
input signal information.
The output voltage can be set in 100 mV steps between 3.5 V and 2.1 V, and in 50 mV steps between 2.05 V
and 1.3 V.
When all D/A input pins VD4 through VD0 (pin 18 through pin 14) are set to “H” level, the DC/DC converter
output voltage is 0 V.
14
MB3828
2. Protection Functions
(1) VCC under voltage lockout circuit (UVLO)
Power surges at power-on, or momentary under-voltage situations can cause abnormal operation in the
MB3828, which may lead to damage or deterioration in systems. This circuit prevents abnormal operation
during times of low voltage by using the supply voltage to detect the level of the internal reference voltage, and
fixes output pins OUT1 (pin 8) and OUT2 (pin 11) to “L” level. Once the supply voltage recovers to a level
above the threshold voltage of the under voltage lockout circuit, operation is restored.
(2) Timer-latch short-circuit protection circuit (SCP)
This circuit detects the output voltage level from Error Amp. and activates the timer circuit, charging the external
capacitor from the CSCP pin (pin 22) when Error Amp. output voltage level reaches or exceeds about 2.1 V.
If Error Amp. output does not return to the normal voltage range before the capacitor voltage reaches about
0.68 V, the latch circuit is activated and the output pins (OUT1, OUT2) are held at “L” level. Once the protector
circuit is activated, it can be reset by switching the power supply off and on again.
(3) Overvoltage protection circuit (OVP)
When the DC/DC converter output voltage (VO) exceeds the output voltage set by the VD4 to VD0 pins by
more than +17.5%, the overvoltage protection circuit output signal goes to “H” level causing one output pin
(OUT1) to be held at “L” level and the other output pin (OUT2) to be held at “H” level.
(4) PWRGOOD comparator detection circuit (PWRGD)
The PWRGOOD pin (pin 21) outputs an “H” level signal as long as the VSENSE pin (pin 20) is receiving the
DC/DC converter output voltage (VO) within the range of 0.9 to 1.1 times the output voltage set by the VD4 to
VD0 pins.
3. Soft Start/Discharge Control
(1) Soft start circuit (CS)
Connecting a capacitor to the CS pin (pin 4) prevents the inrush current at power turnon. Using an Error Amp.
for detecting the soft error allows the soft start time to be initiated independent of output load from the DC/DC
converter.
(2) Discharge control ON/OFF circuit (CTL LOGIC)
Entering an “L” level signal at the CTL pin while an “H” level signal is input at the ENB pin causes the discharge
control ON/OFF circuit (CTL LOGIC) to switch the soft start circuit (CS) from charging to discharging.
The resistance (RS) connected to the RS pin (pin 2) charges the soft start capacitor (CS), so that Error Amp.
provides control over the DC/DC converter output voltage in the same way as during a soft start. This makes
it possible to control voltage drop independently of output load.
When the CS pin voltage reaches the discharge control comparator circuit (CS Comp.) threshold voltage
(≅ 50 mV), the discharge control is canceled.
When an “L” level signal is input at the ENB pin (pin 7), the DC/DC converter output voltage discharge time
control is switched OFF.
15
MB3828
■ METHOD OF SETTING THE SOFT START TIME
At startup of the MB3828, the capacitor (CS) connected to the CS pin begins charging. This produces a soft
start, by providing output voltage from Error Amp. that is proportional to the CS pin voltage regardless of the
DC/DC converter load current.
Soft start time (time to output setting voltage VD)
tS (sec) ~
VD × CS (µF)
2 (µA)
■ TIME SETTING BY SHORT DETECTION
When load conditions change rapidly with the reduced output voltage, as when a load fault occurs, the Capacitor
Cscp connected to the CSCP pin (pin 22) is charged to threshold voltage (VTH:=0.68V) and sets a latch, the
external FET is turned off (inactive interval 100%).
Short detection time
tPE (sec) ~ 0.68 × CSCP (µF) / 2 (µA)
■ OSCILLATOR FREQUENCY SETTING
The oscillator frequency can be set by connecting resistance to the RT pin (pin 1).
Oscillator frequency
fOSC (kHz) ~ 26250 / RT (kΩ)
■ METHOD OF SETTING THE DISCHARGE TIME
• An “L” level CTL signal while the ENB pin is set to “H” level causes the resistance (RS) connected to the RS
pin to discharge electrical charge the capacitor (CS) connected to the CS pin, causing the output voltage to
fall gradually regardless of the DC/DC converter load current.
Discharge time (time to 0.05 V output voltage)
toff (msec) ~ RS (kΩ) × CS (µF) × ln (
VD
)
VTH (CS COMP)
• As long as the ENB pin is set to “L” level, the discharge control function is switched OFF.
■ D/A BLOCK VD4 to VD0 SWITCHING
• Switching of the VD4 to VD0 pin signal during the MB3828 operation may cause transient fluctuation in output
voltage from the DC/DC converter. The resulting voltage instability may cause an “L” level from the PWRGOOD
block, activating the OVP protection and shutting off the output from the DC/DC converter.
To switch VD4 to VD0 pin settings, first input an “L” level control signal to the CTL pin to place the MB3828
in standby status.
• When all VD4 to VD0 pin signals are set to “H” level, the DC/DC converter output is switched OFF.
16
MB3828
■ PWRGOOD COMPARATOR CIRCUIT, OVP CIRCUIT OPERATION TIMING CHART
CTL signal
DC/DC
output voltage
VD × 1.1
VD × 0.9
VD × 1.175
VD × 0.9
PWRGOOD signal
OUT1 signal
OUT2 signal
Operation when ENB signal is “High”.
VD × 1.175
DC/DC
output voltage
VD × 1.1
VD × 0.9
Hysteresis voltage 30 mV
Hysteresis voltage 30 mV
Hysteresis voltage 30 mV
PWRGOOD
OUT2
17
MB3828
■ CTL LOGIC CIRCUIT OPERATION TIMING CHART
CTL signal
ENB signal
VREF output voltage
CS pin voltage
DC/DC
output voltage
0.05 V
ts
toff
■ DC/DC CONVERTER INPUT VOLTAGE (Vin) AND VB VOLTAGE SETTING
The voltage at the CB pin is bootstrapped from the VS pin voltage by an amount equivalent to the VB pin voltage,
as a result of the bootstrap capacitance (CB) between the CB pin and VS pin. Therefore, either the Vin voltage
or VB pin voltage should be adjusted so that the sum of the DC/DC converter block input voltage Vin plus the
VB pin voltage does not exceed the recommended operating conditions for the CB pin boot voltage (VCB).
VB
13
*1
10
Drive
1
8
9
DC/DC converter block
CB
*2
OUT1
VS
CB
Vin
VB
VO
Drive
2
OUT2
*2
11
PGND
12
*1: To connect the external low VF diode (Schottky barrier diode) makes VB pin voltage drop reduced
and then can perform the higher efficiency.
*2: The switching noise can be reduced (0Ω to 5Ω) by connecting the resistance when the external
MOSFET gate input capacitance (Ciss) is large, caused by the external MOSFET gate drive
current limiting resistance.
18
MB3828
■ DC/DC CONVERTER SWITCHING OPERATION WAVEFORMS
<VCC = 5 V, VB = 5 V, Vin = 15V>
VD4–VD0 = 00101 (1.8 V)
load: 2 A
fosc = 200 kHz setting
VS (V)
20
OUT1 (V) OUT2 (V)
15
60
30
50
25
10
40
20
5
30
15
0
20
10
−5
10
5
0
0
−10
−5
VS 5 V
10 V
OUT1
OUT2
1 µs
5V
0
4
2
6
8
10
t (µs)
expansion
VS (V)
1
OUT1 (V) OUT2 (V)
0.5
60
30
50
25
0
40
20
−0.5
30
15
−1
20
10
10
5
0
0
−10
−5
10 V
500 mV
500 mV
10 V
VS
VS
OUT1
OUT1
OUT2
5V
0
0.2
OUT2
5V
100 ns
0.4
0.6
0.8
Synchronous rectifier length: 250 ns (typ)
OUT1 tf: 60 ns (typ)
OUT2 tr: 130 ns (typ)
1.0 0
t (µs)
100 ns
0.2
0.4
0.6
0.8
1.0
t (µs)
Synchronous rectifier length: 200 ns (typ)
OUT1 tr: 130 ns (typ)
OUT2 tf: 100 ns (typ)
19
20
VIN
15 V
VB
5V
5
2
VD4 18
VD3 17
VD2 16
VD1 15
VD0 14
4
4700 pF
CS
100 kΩ
RS
12000 pF
FB
6
10 kΩ
2.4 kΩ
–IN
D/A
(5-bit)
CS
–
+
+
OSC
Error
Amp.
VSENSE
C
(40 pF)
20
1
RT
130 kΩ
VSCP
VB
–
+
–
+
SCP
Comp.
VCS
PWM
Comp.2
Over voltage
protection
(17.5%)
OVP
PWM
+ Comp.1
+
DTC
–
POWERGOOD
PWRGD (±10%)
PWRGOOD
21
CS
Comp.
22
2200 pF
CSCP
SCP
–
+
4.7 kΩ
UVLO
24
0.1 µF
VREF
(3.5 V)
3
SGND
Power
ON/OFF
CTL
bias
Ref
bias
CTL
LOGIC
Drive
2
Drive
1
10
PGND
OUT2
0.1 µF
VS
OUT1
CB
23
VCC
100 µF
Si4410DY
0.1 µF
4.7 µF
VO
150 µF × 6
7.6 µH
RB051L - 40
(24 pins)
220 µF
Si4410DY VS
Note: Si4410DY : Product of Siliconix Co.
RB415D : Product of ROHM Co., LTD.
RB051L-40 : Product of ROHM Co., LTD.
0.1 µF
7 ENB
19 CTL
12
11
9
8
VB
RB415D
13
MB3828
■ APPLICATION EXAMPLE
Output voltage setting signals
MB3828
■ REFERENCE DATA
Conversion efficiency vs. Load current characteristics
(Output voltage = 1.8 V )
100
95
Conversion efficiency η (%)
90
85
80
75
Vin = 15 V
Vin = 11 V
Vin = 22 V
70
Vin = 7 V
65
60
55
50
0.01
0.10
1.00
10.00
Load current (A)
Conversion efficiency vs. Load current characteristics
(Output voltage = 3.3 V )
100
95
Conversion efficiency η (%)
90
85
80
Vin = 15 V
Vin = 22 V
Vin = 11 V
75
Vin = 7 V
70
65
60
55
50
0.01
0.10
1.00
10.00
Load current (A)
(Continued)
21
MB3828
Transient response for CTL ON/OFF
< Output = 1.8 V, nonload >
CS = 4700 pF
ENB = VCC
1V
VO (V)
3
2
1
0
10
CTL (V)
5
0
2 mS
5V
0
4
8
12
16
20
t (ms)
Transient response for CTL ON/OFF
< Output = 3.3 V, nonload >
VO (V)
CS = 2700 pF
ENB = VCC
1V
3
2
1
0
10
CTL (V)
5
0
2 mS
5V
0
4
8
12
16
20
t (ms)
(Continued)
22
MB3828
(Continued)
Transient response for CTL ON/OFF
(Output = 1.8 V)
VO (mV)
100
50 mV
50
0
IO(A)
−50
4
2
0
−2
100µs
10 mV
0
200
400
600
800
1000
t (µs)
Transient response for load abrupt change
(Output = 3.3 V)
VO (mV)
100
50 mV
50
0
IO(A)
−50
4
2
0
−2
100µs
10 mV
0
200
400
600
800
1000
t (µs)
23
MB3828
■ USAGE PRECAUTIONS
1. Device settings must not exceed absolute maximum ratings.
Usage under conditions exceeding absolute maximum ratings may permanently damage LSI devices.
Note also that in normal operation usage within recommended operating conditions is preferred, and that the
reliability of LSI devices may be adversely affected when used outside these conditions.
2. Devices should be used within recommended operating conditions.
Recommended operating conditions are recommended values within which the LSI device is warranted to
operate normally.
Rated values of electrical characteristics are warranted within the range of recommended operating conditions
and within the conditions listed in the condition column for each parameter.
3. Printed circuit board ground lines should be designed in consideration of common
impedance values.
4. Observe precautions against static electricity.
• Containers in which semiconductors are placed should either be protected against static electricity, or be of
conductive material.
• After mounting of devices, use conductive bags or conductive containers when storing or transporting printed
circuit boards.
• Working surfaces, tools and instruments should be properly grounded.
• Workers should be grounded by a ground line with 250 kΩ to 1 MΩ resistance in series between the worker
and ground.
■ ORDERING INFORMATION
Part number
MB3828 PFV-G-BND
24
Package
24-pin Plastic SSOP
(FPT-24P-M03)
Remarks
MB3828
■ PACKAGE DIMENSION
24-pin Plastic SSOP
(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)
25
MB3828
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/
F9903
 FUJITSU LIMITED Printed in Japan
26
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.