LT1641CS8#TRPBF Linear Technology, LT1641CS8#TRPBF Datasheet - Page 7

• Manufacturer Part Number: LT1641CS8#TRPBF
• Description: IC CTRLR HOTSWAP POS VOLT 8SOIC
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LT1641CS8#TRPBF

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 9 V ~ 80 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Family Name: LT1641
• Package Type: SOIC N
• Operating Supply Voltage (min): 9V
• Operating Supply Voltage (max): 80V
• 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: Lead free / RoHS Compliant

TI I G DIAGRA S
APPLICATIO S I FOR ATIO
Hot Circuit Insertion
When circuit boards are inserted into a live backplane, the
supply bypass capacitors on the boards draw high peak
currents from the backplane power bus as they charge up.
The transient currents can permanently damage the con-
nector pins and glitch the system supply, causing other
boards in the system to reset.
The LT1641 is designed to turn on a board’s supply
voltage in a controlled manner, allowing the board to be
safely inserted or removed from a live backplane. The chip
also provides undervoltage and overcurrent protection
while a power good output signal indicates when the
output supply voltage is ready.
Power-Up Sequence
The power supply on a board is controlled by placing an
external N-channel pass transistor (Q1) in the power path
(Figure 5). Resistor R
capacitor C1 provides control of the GATE slew rate.
Resistor R6 provides current control loop compensation
while R5 prevents high frequency oscillations in Q1.
Resistors R1 and R2 provide undervoltage sensing.
W U
GATE
ON
1.313V
Figure 2. ON to GATE Timing
5V
U
t
PLHON
S
provides current detection and
U
W
V
CC
W
– SENSE
GATE
1.233V
Figure 4. SENSE to GATE Timing
1V
U
t
PHLON
47mV
1641 F02
V
CC
t
PHLSENSE
After the power pins first make contact, transistor Q1 is
turned off. If the voltage at the ON pin exceeds the turn-on
threshold voltage, the voltage on the V
undervoltage lockout threshold, and the voltage on the
TIMER pin is less than 1.233V, transistor Q1 will be turned
on (Figure 6). The voltage at the GATE pin rises with a slope
equal to 10µA/C1 and the supply inrush current is set at
I
sense resistor R
be limited by the internal current limit circuitry which
adjusts the voltage on the GATE pin to maintain a constant
voltage across the sense resistor.
Once the voltage at the output has reached its final value,
as sensed by resistors R3 and R4, the PWRGD pin goes
high.
Short-Circuit Protection
The LT1641 features a programmable foldback current
limit with an electronic circuit breaker that protects against
short-circuits or excessive supply currents. The current
limit is set by placing a sense resistor between V
and SENSE (Pin 7).
INRUSH
PWRGD
FB
= C
L
• 10µA/C1. If the voltage across the current
Figure 3. FB to PWRGD Timing
S
1.313V
gets too high, the inrush current will then
1V
1641 F04
t
PLHFB
CC
1.233V
pin exceeds the
LT1641
1V
CC
t
PHLFB
1641 F03
(Pin 8)
1641fd
7