DS04-27217-5E
FUJITSU SEMICONDUCTOR
DATA SHEET
ASSP For Power Supply Applications
Pentium
DC/DC Converter IC
MB3828
s
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.
s
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
A TYP
On-chip PWRGOOD circuit for output voltage state detection
Timer-latch short-circuit protection circuit, and overvoltage protection circuit for output protection
s
PACKAGE
24-pin Plastic SSOP
(FPT-24P-M03)
3
MB3828
s
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
V
CC
--
Power supply pin for reference power and control circuit
24
VREF
O
Reference voltage output pin
PDF 
ZIP
