LTC1477/LTC1478
Single and Dual Protected
High Side Switches
FEATURES
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTION
The LTC
廬
1477/LTC1478 protected high side switches
provide extremely low R
DS(ON)
switching with built-in
protection against short-circuit and thermal overload con-
ditions. A built-in charge pump generates gate drive
higher than the supply voltage to fully enhance the internal
NMOS switch. This switch has no parasitic body diode and
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.)
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擄C.
The LTC1477 single is available in 8-lead SO packaging.
The LTC1478 dual is available in 16-lead SO packaging.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Extremely Low R
DS(ON)
Switch: 0.07
鈩?/div>
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: 0.01碌A
Built-In Charge Pump
Controlled Rise and Fall Times: t
R
= 1ms
Single Switch in 8-Pin SO Package
Dual Switch in Narrow 16-Pin SO Package
APPLICATIONS
s
s
s
s
s
s
Notebook Computer Power Management
Power Supply/Load Protection
Supply/Battery Switch-Over Circuits
Circuit Breaker Function
"Hot Swap" Board Protection
Peripheral Power Protection
SI PLIFIED BLOCK DIAGRAM
V
INS
V
IN1
V
IN2
V
IN3
5.20
OUTPUT VOLTAGE (V)
GATE CHARGE
AND
DISCHARGE
CONTROL LOGIC
5.10
T
A
= 25擄C
V
IN1
= V
IN2
= V
IN3
= V
INS
= 5V
*
*
*
5.00
4.90
4.80
4.70
4.60
EN
CHARGE
PUMP
CURRENT LIMIT
AND THERMAL
SHUTDOWN
V
OUT
0
*NMOS SWITCHES WITH NO PARASITIC BODY DIODES
LTC1477/1478 鈥?TA01
U
W
U
W
Switch Output Voltage
0.25
0.5
0.75 1.00
1.25
OUTPUT CURRENT (A)
1.50
LTC1477/1478 鈥?TP02
1
1
2
3
4
5
6
7
8
