ML4903 Datasheet, PDF (1/12 Pages) Micro Linear Corporation – High Current Synchronous Buck Controller

July 1999
ML4903
High Current Synchronous Buck Controller
GENERAL DESCRIPTION
The ML4903 high current synchronous buck controller
provides high efficiency DC/DC conversion to generate
V_CCP for processors such as the Pentium^® Pro and Pentium
II from Intel^®.
The ML4903 controller, when combined with two external
MOSFETs, generates output voltages between 1.8V and
3.5V from a 12V supply. The output voltage is selected via
an internal 2 chord 4-bit DAC. In the upper range, the
output can be set between 2.1V and 3.5V in 100mV steps.
In the lower range, the output can be set between 1.8V
and 2.05V in 50mV steps. Output currents in excess of
20A can be attained at efficiencies greater than 80%.
The ML4903 can be enabled/disabled via the SHDN pin.
While disabled, the output of the regulator is completely
isolated from the circuit’s input supply. The ML4903
employs fixed-frequency PWM control combined with a
sophisticated control loop enhancement circuit to provide
excellent load transient response.
FEATURES
s Designed to meet Pentium Pro and Pentium II VRM
power supply requirements
s DC regulation to +1% maximum
s Proprietary circuitry provides transient response of ±5%
maximum over a 0A to 14A load range
s Programmable output voltage (1.8V to 3.5V) is set by
an onboard 2 chord 4-bit DAC
s Synchronous buck topology for maximum power
conversion efficiency
s Fixed frequency operation for easier system integration
s Integrated anti-shootthrough logic, short circuit
protection, shutdown, and UV lockout
BLOCK DIAGRAM
VDD
19
+
10.5V ^–
VCC
18
+
4.4V ^–
UVLO
5V
30µA
PROTECT
20
3.5V +
–
SHDN
6
D0
1
D1
2
D2
3
D3
4
RANGE
5
2 CHORD
4 BIT DAC
VDAC
VDAC + 3%
+
–
VFB
+
VDAC - 3%
–
CONTROL
LOGIC
+
–
200kHz
VDAC + 10%
+
VDAC + 3%
–
VFB
+
VDAC - 10%
–
VDAC - 3%
P DRV
17
N DRV
16
PWR GND
15
COMP
13
VFB
11
VDAC
-107mV _ISENSE
12
PWR GOOD
8
3.5V
REFERENCE
VREF
9
GND
10
1