LTC1477CS8 Linear Technology, LTC1477CS8 Datasheet - Page 5

• Manufacturer Part Number: LTC1477CS8
• Description: IC HI-SIDE SWITCH PROT SNGL8SOIC
• Manufacturer: Linear Technology
• Type: High Sider

Specifications of LTC1477CS8

• Input Type: Non-Inverting
• Number Of Outputs: 1
• On-state Resistance: 70 mOhm
• Current - Peak Output: 2A
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output / Channel: -

BLOCK
APPLICATIONS
Tailoring I
The LTC1477 is designed to current limit at approximately
2A during a short circuit with all the V
the input power supply. It is possible however, to reduce
this current by selectively disconnecting two of the four
power supply pins (V
of disconnecting these pins on R
current limit
Input TTL-CMOS Converter
The LTC1477 enable input is designed to accommodate a
wide range of 3V and 5V logic families. The input threshold
voltage is approximately 1.4V with 100mV of hysteresis.
The input enables the bias generator, the gate charge
pump and the protection circuitry. Therefore, when the
enable input is turned off, the entire circuit is powered
down and the supply current drops below 1 A.
Ramped Switch Control
The LTC1477 gate charge pump includes circuitry which
ramps the NMOS switch on slowly (1ms typical rise time)
but turns it off much more quickly (typically 20 s).
Bias, Oscillator and Gate Charge Pump
When the switch is enabled, a bias current generator and
high frequency oscillator are turned on. The on-chip
capacitive charge pump generates approximately 12V of
OPERATION
EN
LIMIT
DIAGRAM
and R
TTL-TO-CMOS
CONVERTER
U
U
IN2
(LTC1477 or single channel of LTC1478)
DS(ON)
and V
INFORMATION
U
W
for Load Requirements
IN3
(LTC1477 or single channel of LTC1478)
). Table 1 lists the effects
DS(ON)
OSCILLATOR
AND BIAS
W
IN
pins connected to
and short-circuit
U
CONTROL LOGIC
GATE CHARGE
DISCHARGE
CHARGE
PUMP
V
AND
INS
gate drive for the internal low R
the power supply. No external 12V supply is required to
switch the output.
Switch Protection
Two levels of protection are designed into the power
switch in the LTC1477. The switch is protected against
accidental short circuits with a current limit circuit which
limits the output current to typically 2A when the output is
shorted to ground. The LTC1477 also has thermal shut-
down set at approximately 130 C which limits the power
dissipation to safe levels.
LTC1478 Operation
The LTC1478 dual protected switch can be thought of as
two independent LTC1477 single protected switches. The
input supply voltages may be from separate power sources.
The ground connection, however, is common to both
channels and must be connected to the same potential.
Table 1. Effects of Disconnecting V
R
I
Note: 5V Operation
Note that there is an inverse relationship between output
current limit and switch resistance. This allows the tailor-
LIMIT
DS(ON)
CURRENT LIMIT
AND THERMAL
SHUTDOWN
ALL V
CONNECTED
0.07
2A
IN
PINS
V
IN1
LTC1477/LTC1478
DISCONNECTED
V
IN2
0.09
V
1.5A
DS(ON)
IN3
V
LTC1477/1478 • BD01
IN3
IN2
NMOS switch from
and V
V
OUT
DISCONNECTED
V
IN2
IN3
0.12
0.85A
AND V
IN3
5