MAX798 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – High-Accuracy Step-Down Controller with Synchronous Rectifier for CPU Power

19-1175; Rev 0; 12/96
High-Accuracy Step-Down Controller
with Synchronous Rectifier for CPU Power
_______________General Description
The MAX798^† high-performance, step-down DC-DC
converter provides main CPU power in battery-powered
systems. This buck controller achieves 96% efficiency
by using synchronous rectification and Maxim’s propri-
etary Idle Mode™ control scheme to extend battery life
at full-load (up to 10A) and no-load outputs. The
MAX798’s high accuracy meets the demanding require-
ments of the latest-generation CPUs. Excellent dynamic
response corrects output transients 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 crow-
bar switching currents found in some PMOS/NMOS switch
designs.
The MAX798 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.
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
__________________Pin Configuration
TOP VIEW
SS ₁
SKIP 2
REF 3
GND 4
SYNC 5
SHDN 6
FB 7
CSH 8
MAX798
SO
16 DH
15 LX
14 BST
13 DL
12 PGND
11 VL
10 V+
9 CSL
____________________________Features
o 96% Efficiency
o 4.5V to 30V Input Range
o 1.6V to 6V Adjustable Precision Output
o ±0.4% Max Total Load-Regulation Error
o 0.06%/V Max Line-Regulation Error
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 1.2mA Typical Quiescent Current
(V_IN = 12V, V_OUT = 2.5V)
o 1µA Typical Shutdown Current
______________Ordering Information
PART
MAX798ESE
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 Narrow SO
__________Typical Operating Circuit
INPUT
4.5V TO 30V
5V, 25mA
4.7µF
V+ VL
BST
DH
MAX798
LX
N
0.1µF
R_SENSE
V_OUT
ON
SHDN
DL
N
OFF
PGND
CSH
CSL
GND ^FB
Idle Mode is a trademark of Maxim Integrated Products.
†_{U.S. and foreign patents pending.}
________________________________________________________________ Maxim Integrated Products 1
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