LTC1645CS8 Linear Technology, LTC1645CS8 Datasheet - Page 13

• Manufacturer Part Number: LTC1645CS8
• Description: IC CTRLR SEQ HOTSWAP DUAL 8SOIC
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC1645CS8

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 1.2 V ~ 12 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Linear Misc Type: Positive Low Voltage
• Family Name: LTC1645
• Package Type: SOIC N
• Operating Supply Voltage (min): 1.2V
• Operating Supply Voltage (max): 12V
• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Product Depth (mm): 3.99mm
• Product Height (mm): 1.5mm
• Product Length (mm): 5mm
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
V
voltage on the external capacitor C
with a slope dv/dt = 2 A/C
the trip point (1.23V), the timer is reset by pulling the
TIMER pin back to ground. The timer period is
t = (1.23V • C
capacitor.
Electronic Circuit Breaker
The LTC1645 features an electronic circuit breaker func-
tion that protects against short circuits or excessive out-
put currents. By placing sense resistors between the
supply inputs and sense pins of the supplies, the circuit
breaker trips whenever the voltage across either sense
resistor is greater than 50mV for more than 1.5 s. If the
circuit breaker trips, both GATE pins are immediately
pulled to ground and the external N-channels FETs are
quickly turned off (time point 6 in Figure 12). The circuit
breaker resets and another timing cycle starts by taking
CC n
– V
Figure 13. Extending the Short-Circuit Protection Delay
SENSE n
TIMER
GATE n
RESET
V
V
OUT n
CC n
ON
1 2
TIMER
Figure 12. Current Fault Timing
RAMPING UP
)/2 A. For a 200ms delay, use a 0.33 F
3
U
V
4
CC n
C
F
SENSE n
TIMER
LTC1645
U
CURRENT
5
FAULT
R
F
6
. When the voltage reaches
GATE n
7
TIMER
W
AND RAMP UP
RESET FAULT
8
1645 G13
starts to ramp up
9
1645 F12
10
U
ON
the ON pin below 0.4V and then high as shown at time
point 7.
At the end of the timer cycle (time point 8), the charge
pump turns on again. If the circuit breaker feature is not
required, short the SENSE n pin to V
If the 1.5 s response time is too fast to reject supply noise,
add external resistors and capacitors R
sense circuit as shown in Figure 13.
The ON Pin
The ON pin is used to control system operation as shown
in Figure 14. At time point 1, the board makes connection
and the supplies power up the chip. At time point 2, the ON
pin goes high and a timer cycle starts as long as both V
pins are higher than the undervoltage lockout trip point
(2.23V for V
fault is not detected. At the end of the timer cycle (time
point 3), the charge pump is turned on and the GATE n pin
voltages start to ramp up with the output supply voltages,
V
At time point 4, V
(this example assumes the FB pin resistive divider is
connected to V
of the timing cycle (time point 5), RESET goes high and the
power-up process is complete.
TIMER
RESET
GATE1
GATE2
V
V
V
OUT n
OUT1
OUT2
CC n
0.8V
0.4V
0V
2V
, following one gate-to-source voltage drop lower.
1 2
RAMPING UP AND
DOWN TOGETHER
3
CC1
4
OUT2
5
Figure 14. ON Pin Waveforms
and 1.12V for V
OUT2
6 7
) and a timing cycle starts. At the end
reaches its power-good trip level
8
9
DOWN SEPARATELY
RAMPING UP AND
10 11 12 13 14 15 16 17 18 19 20
CC2
) and an overcurrent
CC n
.
F
LTC1645
and C
TURNING OFF FAST
RAMPING UP AND
F
13
to the
1645fa
1645 F14
CC