LTC1477/LTC1478
Single and Dual Protected
High Side Switches
U
FEATURES
DESCRIPTION
The LTC®1477/LTC1478 protected high side switches
provide extremely low RDS(ON) switching with built-in
protectionagainstshort-circuitandthermaloverloadcon-
ditions. A built-in charge pump generates gate drive
higherthanthesupplyvoltagetofullyenhancetheinternal
NMOSswitch. Thisswitchhasnoparasiticbodydiodeand
therefore no current flows through the switch when it is
turned off and the output is forced above the input supply
voltage. (DMOS switches have parasitic body diodes that
become forward biased under these conditions.)
■
Extremely Low RDS(ON) Switch: 0.07
Ω
■
No Parasitic Body Diode
■
Built-In Short-Circuit Protection: 2A
■
Built-In Thermal Overload Protection
■
Operates from 2.7V to 5.5V
■
Inrush Current Limited
■
Ultralow Standby Current: 0.01µA
■
Built-In Charge Pump
Controlled Rise and Fall Times: tR = 1ms
Single Switch in 8-Pin SO Package
■
■
■
Dual Switch in Narrow 16-Pin SO Package
Two levels of protection are provided by the
LTC1477/LTC1478. The first level of protection is short-
circuit current limit which is set at 2A. The short-circuit
current can be reduced to as low as 0.85A by disconnect-
ing portions of the power device (see Applications Infor-
mation). The second level of protection is provided by
thermal overload protection which limits the die tempera-
ture to approximately 130°C.
U
APPLICATIONS
■
Notebook Computer Power Management
■
Power Supply/Load Protection
■
Supply/Battery Switch-Over Circuits
■
Circuit Breaker Function
■
"Hot Swap" Board Protection
The LTC1477 single is available in 8-lead SO packaging.
The LTC1478 dual is available in 16-lead SO packaging.
■
Peripheral Power Protection
, LTC and LT are registered trademarks of Linear Technology Corporation.
W
W
SI PLIFIED BLOCK DIAGRAM
V
V
V
V
IN3
INS
IN1
IN2
Switch Output Voltage
5.20
T
= 25°C
A
GATE CHARGE
AND
DISCHARGE
CONTROL LOGIC
V
= V = V = V = 5V
IN1
IN2 IN3 INS
5.10
5.00
4.90
4.80
4.70
4.60
*
*
*
CURRENT LIMIT
AND THERMAL
SHUTDOWN
CHARGE
PUMP
V
EN
OUT
0
0.5
0.75 1.00
1.25 1.50
0.25
OUTPUT CURRENT (A)
*NMOS SWITCHES WITH NO PARASITIC BODY DIODES
LTC1477/1478 • TA01
LTC1477/1478 • TP02
1