MAX797H Datasheet, PDF (1/8 Pages) Maxim Integrated Products – High-Voltage, Step-Down Controller with Synchronous Rectifier for CPU Power

19-1239; Rev 0; 7/97
High-Voltage, Step-Down Controller with
Synchronous Rectifier for CPU Power
_______________General Description
The MAX797H high-performance, step-down DC-DC
converter provides main CPU power in battery-powered
systems. A 40V rating on the power stage’s input allows
operation with high-cell-count batteries and a wide
range of AC adaptors. This buck controller achieves
96% efficiency by using synchronous rectification and
Maxim’s proprietary Idle Mode™ control scheme to
extend battery life at full-load (up to 10A) and no-load
outputs. Excellent dynamic response corrects output tran-
sients caused by the latest dynamic-clock CPUs within five
300kHz clock cycles. Unique bootstrap circuitry drives
inexpensive N-channel MOSFETs, reducing system cost
and eliminating the crowbar switching currents found in
some PMOS/NMOS switch designs.
The MAX797H has a logic-controlled and synchronizable
fixed-frequency, pulse-width-modulating (PWM) operating
mode, which reduces noise and RF interference in sensi-
tive mobile-communications and pen-entry applications.
The SKIP override input allows automatic switchover to
idle-mode operation (for high-efficiency pulse skipping) at
light loads, or forces fixed-frequency mode for lowest noise
at all loads. The MAX797H is pin compatible with the popu-
lar MAX797, but has a higher input voltage range.
The MAX797H comes in a 16-pin narrow SO package.
________________________Applications
Notebook and Subnotebook Computers
Industrial Controls
__________________Pin Configuration
TOP VIEW
SS 1
SKIP 2
REF 3
GND 4
SYNC 5
SHDN 6
FB 7
CSH 8
MAX797H
SO
16 DH
15 LX
14 BST
13 DL
12 PGND
11 VL
10 V+
9 CSL
____________________________Features
o 96% Efficiency
o Up to 40V Power Input
o 2.5V to 6V Adjustable Output
o Preset 3.3V and 5V Outputs (at up to 10A)
o 5V Linear-Regulator Output
o Precision 2.505V Reference Output
o Automatic Bootstrap Circuit
o 150kHz/300kHz Fixed-Frequency PWM Operation
o Programmable Soft-Start
o 375µA Quiescent Current (V_IN = 12V, V_OUT = 5V)
o 1µA Shutdown Current
______________Ordering Information
PART^†
TEMP. RANGE
MAX797HESE
-40°C to +85°C
†_{U.S. and foreign patents pending.}
PIN-PACKAGE
16 Narrow SO
__________Typical Operating Circuit
+4.5V TO +30V
SUPPLY
INPUT
V+
SHDN
VL
DH
MAX797H _BST
+4V TO +40V
POWER INPUT
+3.3V
OUTPUT
SS
LX
REF
DL
PGND
SYNC
GND
SKIP
CSH
CSL
FB
Idle Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products 1
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