a
High Efficiency Synchronous
Step-Down Switching Regulators
ADP1148, ADP1148-3.3, ADP1148-5
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Operation From 3.5 V to 18 V Input Voltage
Ultrahigh Efficiency > 95%
Low Shutdown Current
Current Mode Operation for Excellent Line and Load
Transient Response
High Efficiency Maintained Over Wide Current Range
Logic Controlled Micropower Shutdown
Short Circuit Protection
Very Low Dropout Operation
Synchronous FET Switching for High Efficiency
Adaptive Nonoverlap Gate Drives
ADJUSTABLE
VERSION
PWR SIGNAL
VIN P-DRIVE N-DRIVE GND
GND SENSE(+) VFB SENSE(–)
3
12
14
11
NON-OVERLAP
DRIVE
8
9
7
V
2
R
Q S
TE
SLEEP
B
1
S
APPLICATIONS
Notebook and Palmtop Computers
Portable Instruments
Battery Operated Digital Devices
Industrial Power Distribution
Avionics Systems
Telecom Power Supplies
GPS Systems
Cellular Telephones
1
ADP1148
VTH1
VTH2
Q R
S
C
OFF-TIME
CONTROL
LE
13k⍀
10mV to
150mV
T
G
VIN
SENSE(–)
VFB
100k⍀
1.25V
REFERENCE
4
GENERAL DESCRIPTION
10
5
ITH
SHUTDOWN
INT VCC
The constant off-time architecture maintains constant ripple
current in the inductor, easing the design of wide input range
converters. Current-mode operation provides excellent line and
load transient response. The operating current level is user
programmable via an external current sense resistor.
B
SO
The ADP1148 is part of a family of synchronous step-down
switching regulator controllers featuring automatic sleep mode
to maintain high efficiencies at low output currents. These
devices drive external complementary power MOSFETs at
switching frequencies up to 250 kHz using a constant off-time
current-mode architecture.
6
CT
The ADP1148 incorporates automatic Power Saving Sleep
Mode operation when load currents drop below the level required for continuous operation. In sleep mode, standby power
is reduced to only about 2 mW at VIN = 10 V. In shutdown,
both MOSFETs are turned off.
TYPICAL APPLICATIONS
VIN (5.2V TO 18V)
1F
CIN
100F
VIN
10nF
0V = NORMAL
>1.5V = SHUTDOWN
ADP1148
L* RSENSE**
62H 0.05⍀
SHUTDOWN
ITH
VOUT
5V/2A
SENSE(+)
CT
SENSE(–)
1000pF
RC
1k⍀
CC
3300pF
CT
470pF
N-DRIVE
S-GND
P-GND
100
VIN = 6V
95
P-CH
IRF7204
P-DRIVE
O
INT VCC
+
+
N-CH
IRF7403
COUT
390F
VIN = 10V
EFFICIENCY – %
+
90
85
80
75
FIGURE 1 CIRCUIT
C1
10BQ040
70
0.02
0.2
LOAD CURRENT – A
2
*COILTRONICS CTX-68-4
**KRL SL-1-C1-0R050L
Figure 1. High Efficiency Step-Down Converter
Figure 2. ADP1148-5 Typical Efficiency
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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Tel: 781/329-4700
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Fax: 781/326-8703
© Analog Devices, Inc., 1997
