LTC1644CGN#TR Linear Technology, LTC1644CGN#TR Datasheet - Page 11

• Manufacturer Part Number: LTC1644CGN#TR
• Description: IC CONTROLLER HOT SWAP 20-SSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC1644CGN#TR

• Applications: CompactPCI™
• Internal Switch(s): No
• Voltage - Supply: 3.3V, 5V, ±12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP (0.154", 3.91mm Width)
• Family Name: LTC1644
• Package Type: SSOP N
• Operating Supply Voltage (min): 2.75/10.8/-10.8V
• Operating Supply Voltage (max): 13.2/-14V
• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Product Depth (mm): 3.99mm
• Product Height (mm): 1.5mm
• Mounting: Surface Mount
• Pin Count: 20
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC1644CGNTR

APPLICATIO S I FOR ATIO
Hot Circuit Insertion
When a circuit board is inserted into a live CompactPCI
(CPCI) slot, the supply bypass capacitors on the board can
draw huge supply transient currents from the CPCI power
bus as they charge up. The transient currents can cause
glitches on the power bus, causing other boards in the
system to reset.
The LTC1644 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 CPCI slot without
glitching the system power supplies. The chip also protects
the supplies from shorts, precharges the bus I/O pins during
insertion and extraction and monitors the supply voltages.
The LTC1644 is specifically designed for CPCI applica-
tions where the chip resides on the plug-in board.
LTC1644 Feature Summary
• Allows safe board insertion and removal from a CPCI
• Controls all four CPCI supplies: –12V, 12V, 3.3V and 5V.
• Adjustable foldback current limit: an adjustable analog
• 12V and –12V circuit breakers: if either supply remains
• Dual-level, adjustable 5V and 3.3V circuit breakers: if
TI I G DIAGRA S
backplane.
current limit with a value that depends on the output
voltage. If the output is shorted to ground, the current
limit drops to keep power dissipation and supply glitches
to a minimum.
in current limit too long, the circuit breaker will trip, the
supplies are turned off and the FAULT pin is pulled low.
either supply exceeds current limit for too long, the
circuit breaker will trip, the supplies will be turned off
and the FAULT pin will be asserted. In the event that
W U
V
5VSENSE
V
3VSENSE
FAULT
t
OC
OR
Overcurrent Fault Detect
U
5V OR 3.3V
100mV
U
W
FALL TIME
5V
IN
t
1644 TD01
OC
= 5V, 3V
W
1 s
IN
= 3.3V
U
• Current limit during power up: the supplies are allowed
• 12V and –12V power switches on chip.
• PWRGD output: monitors the voltage status of the four
• PCI_RST# combined on-chip with HEALTHY# to create
• Precharge output: on-chip reference and amplifier pro-
• Space saving 20-pin SSOP package.
CPCI Power Requirements
CPCI systems usually require four power rails: 5V, 3.3V,
12V and –12V. The tolerance of the supplies as measured
at the components on the plug-in card is summarized in
Table 1.
Table 1. Compact PCI Power Specifications
either supply exceeds 3 times the nominal current level,
all supplies will be turned off and the FAULT pin will be
asserted immediately.
to power up in current limit. This allows the chip to
power up boards with widely varying capacitive loads
without tripping the circuit breaker. The maximum
allowable power-up time is adjustable using the TIMER
pin.
supply voltages.
LOCAL_PCI_RST# output. If HEALTHY# deasserts,
LOCAL_PCI_RST# is asserted independent of
PCI_RST#.
vide 1V for biasing bus I/O connector pins during CPCI
card insertion and extraction.
SUPPLY
–12V
3.3V
12V
5V
V
5VSENSE
V
3VSENSE
FAULT
t
SC
OR
Short-Circuit Fault Detect
TOLERANCE
+5%/–3%
+5%/–3%
5V OR 3.3V
200mV
5%
5%
FALL TIME
5V
IN
t
1644 TD02
SC
= 5V, 3V
MAX RIPPLE (
LTC1644
10ns
IN
= 3.3V
240mV
240mV
50mV
50mV
11
P-P
)
1644f