LTC1157
3.3V Dual Micropower
High-Side/Low-Side MOSFET Driver
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Allows Lowest Drop 3.3V Supply Switching
Operates on 3.3V or 5V Nominal Supplies
3 Microamps Standby Current
80 Microamps ON Current
Drives Low Cost N-Channel Power MOSFETs
No External Charge Pump Components
Controlled Switching ON and OFF Times
Compatible with 3.3V and 5V Logic Families
Available in 8-Pin SOIC
APPLICATI
s
s
s
s
s
s
s
S
Notebook Computer Power Management
Palmtop Computer Power Management
P-Channel Switch Replacement
Battery Charging and Management
Mixed 5V and 3.3V Supply Switching
Stepper Motor and DC Motor Control
Cellular Telephones and Beepers
The LTC1157 dual 3.3V micropower MOSFET gate driver
makes it possible to switch either supply or ground
reference loads through a low R
DS(ON)
N-channel switch
(N-channel switches are required at 3.3V because P-
channel MOSFETs do not have guaranteed R
DS(ON)
with
V
GS
≤
3.3V). The LTC1157 internal charge pump boosts
the gate drive voltage 5.4V above the positive rail (8.7V
above ground), fully enhancing a logic level N-channel
switch for 3.3V high-side applications and a standard N-
channel switch for 3.3V low-side applications. The gate
drive voltage at 5V is typically 8.8V above supply (13.8V
above ground), so standard N-channel MOSFET switches
can be used for both high-side and low-side applications.
Micropower operation, with 3µA standby current and
80µA operating current, makes the LTC1157 well suited
for battery-powered applications.
The LTC1157 is available in both 8-pin DIP and SOIC.
TYPICAL APPLICATI
Ultra Low Voltage Drop 3.3V Dual High-Side Switch
12
3.3V
GATE VOLTAGE – SUPPLY VOLTAGE (V)
+
10µF
10
8
6
4
2
0
2.0 2.5
V
S
3.3V
LOGIC
IN1
LTC1157
IN2
GND
G2
G1
(8.7V)
(8.7V)
IRLR024
IRLR024
3.3V
LOAD
3.3V
LOAD
LTC1157 • TA01
U
Gate Voltage Above Supply
3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
6.0
LTC1157 • TA02
UO
UO
1
LINER [ LINEAR TECHNOLOGY ]
