LTC1645IS8 Linear Technology, LTC1645IS8 Datasheet - Page 7

• Manufacturer Part Number: LTC1645IS8
• Description: IC CTRLR SEQ HOTSWAP DUAL 8SOIC
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC1645IS8

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 1.2 V ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
Hot Circuit Insertion
When a circuit board is inserted into a live backplane, the
supply bypass capacitors on the board can draw huge
transient currents from the backplane power bus as they
charge. These transient currents can cause permanent
damage to the connector pins and produce glitches on the
system supply, resetting other boards in the system.
The LTC1645 is designed to turn a board’s supply voltages
on and off in a controlled manner, allowing the board to be
safely inserted or removed from a live backplane. The chip
provides a system reset signal and a spare comparator to
indicate when board supply voltages drop below user-
programmable voltages, and a fault signal to indicate if an
overcurrent condition has occurred.
The LTC1645 can be located before or after the connector
as shown in Figure 1. A staggered PCB connector can
sequence pin connections when plugging and unplugging
circuit boards. Alternatively, the control signal can be
generated by processor control.
U
FAULT
V
CC
U
FAULT
V
CC
CONNECTOR
BACKPLANE
ON
W
(b) Hot Swap Controller on Daughterboard
(a) Hot Swap Controller on Motherboard
ON
FAULT
GND
Figure 1. Staggered Pins Connection
V
STAGGERED PCB
EDGE CONNECTOR
CC
U
LTC1645
SENSE
GATE
Power Supply Tracking and Sequencing
Some applications require that the potential difference
between two power supplies not exceed a certain voltage.
This requirement applies during power-up and power-
down as well as during steady state operation, often to
prevent latch-up in a dual supply ASIC. Other systems
require one supply to come up after another, for example,
if a system clock needs to start before a block of logic.
Typical dual supplies or backplane connections may come
up at arbitrary rates depending on load current, capacitor
size, soft-start rates, etc. Traditional solutions are cum-
bersome and require complex circuitry to meet the power
supply requirements.
The LTC1645 provides a simple solution to power supply
tracking and sequencing needs. The LTC1645 guarantees
supply tracking by ramping the supplies up and down
together (see Figure 15). The sequencing capabilities of
the LTC1645 allow nearly any combination of supply
ramping (e.g., see Figure 17) to satisfy various sequenc-
ing specifications. See the Power Supply Tracking and
Sequencing Applications section for more information.
ON
FAULT
GND
V
CC
CONNECTOR
BACKPLANE
LTC1645
SENSE
GATE
STAGGERED PCB
EDGE CONNECTOR
1645 F01
+
C
LOAD
+
V
OUT
C
LOAD
V
OUT
LTC1645
1645fa
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