ML4902 Datasheet, PDF (1/12 Pages) Micro Linear Corporation – High Current Synchronous Buck Controller

May 1998
ML4902
High Current Synchronous Buck Controller
GENERAL DESCRIPTION
The ML4902 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 ML4902 controller, when combined with 2 N-channel
MOSFETs, generates output voltages between 1.8V and
3.5V from a 5V 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 90%.
The ML4902 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 ML4902
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 20A load range
s Programmable output voltage (1.8V to 3.5V) is set by
an onboard 2 chord 4-bit DAC
s Synchronous N-channel 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%
N DRV H
17
N DRV L
16
PWR GND
15
COMP
13
VFB
11
VDAC
–97mV _ISENSE
12
PWR GOOD
8
3.5V
REFERENCE
VREF
9
GND
10
1