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ADM1172 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADM1172
Beschreibung Hot Swap Controller
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 17 Seiten
ADM1172 Datasheet, Funktion
Data Sheet
2.7 V to 16.5 V Hot Swap Controller
with Power-Fail Comparator
ADM1172
FEATURES
Controls supply rails from 2.7 V to 16.5 V
Allows protected board removal and insertion to a live
backplane
External sense resistor provides adjustable analog current
limit with circuit breaker
Peak fault current limited with fast response
Charge pumped gate drive for external N-FET switch
Power-fail comparator
Automatic retry or latch-off during current fault
Undervoltage lockout
8-lead, TSOT package
APPLICATIONS
Hot swap board insertion: line cards, raid systems
Industrial high-side switches/circuit breakers
Electronic circuit breakers
GENERAL DESCRIPTION
The ADM1172 is a hot swap controller that safely enables a
printed circuit board to be removed and inserted to a live
backplane. This is achieved using an external N-channel power
MOSFET with a current control loop that monitors the load
current through a sense resistor. An internal charge pump is
used to enhance the gate of the N-channel FET. When an over-
current condition is detected, the gate voltage of the FET is
reduced to limit the current flowing through the sense resistor.
During an overcurrent condition, the TIMER pin capacitor
determines the amount of time the FET remains at a current
limiting mode of operation until it is shut down. The ON
(ON-CLR) pin is the enable input for the device and can be
used to monitor the input supply voltage. The ADM1172
operates with a supply voltage ranging from 2.7 V to 16.5 V.
The ADM1172 also features a power-fail comparator. The
voltage on the PFI pin is compared with an internal 0.6 V
reference, and the output of this comparator is presented on
the PFO pin. This device is available in two options: the
ADM1172-1 with automatic retry for overcurrent fault and the
ADM1172-2 with latch-off for an overcurrent fault. Toggling
the ON (ON-CLR) pin resets a latched fault. The ADM1172 is
packaged in an 8-lead TSOT.
VIN = 5V
GND
FUNCTIONAL BLOCK DIAGRAM
LONG
RSENSE
Q1
SHORT RON1
RON2
LONG
VCC SENSE
ON GATE
ADM1172-1
PFI
TIMER
GND
CTIMER
PFO
VOUT = 5V
CLOAD
RPR1
RPR2
GND
Figure 1.
Rev. A
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ADM1172 Datasheet, Funktion
Data Sheet
ADM1172
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
ADM1172-1AUJ
TIMER 1
8 VCC
GND 2 TOP VIEW 7 SENSE
PFO 3 (Not to Scale) 6 PFI
ON 4
5 GATE
Figure 2. Pin Configuration, 1AUJ Model
ADM1172-2AUJ
TIMER 1
8 VCC
GND 2 TOP VIEW 7 SENSE
PFO 3 (Not to Scale) 6 PFI
ON-CLR 4
5 GATE
Figure 3. Pin Configuration, 2AUJ Model
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1 TIMER
Timer Input Pin. The initial and circuit breaker timing cycles are set by this external capacitor. The initial timing
delay is 272.9 ms/μF, and 21.7 ms/μF for a circuit breaker delay. When the TIMER pin is pulled beyond the upper
threshold, the GATE turns off.
2 GND
Chip Ground Pin.
3 PFO
Power-Fail Comparator Output. Digital output from the power-fail comparator.
4 ON (ON-CLR) Input Pin. The ON (ON-CLR) pin is an input to a comparator that has a low-to-high threshold of 1.3 V with 80 mV
hysteresis and a glitch filter. The ADM1172 is reset when the ON (ON-CLR) pin is low. When the ON (ON-CLR) pin is
high, the ADM1172 is enabled. A rising edge on this pin has the added function of clearing a fault and restarting
the device on the latched off model, the ADM1172-2.
5 GATE
Gate Output Pin. An internal charge pump provides a 12 μA pull-up current to drive the gate of an N-channel
MOSFET. In an overcurrent condition, the ADM1172 controls the external FET to maintain a constant load
current.
6 PFI
Power-Fail Comparator Input. Comparator threshold = 0.6 V.
7 SENSE
Current Limit Sense Input Pin. The current limit is set via a sense resistor between the VCC and SENSE pins. In an
overcurrent condition, the gate of the FET is controlled to maintain the SENSE voltage at 50 mV. When this limit is
reached, the TIMER circuit breaker mode is activated. The circuit breaker limit can be disabled by connecting the
VCC pin and SENSE pin together.
8 VCC
Positive Supply Input Pin. The ADM1172 operates between 2.7 V to 16.5 V. An undervoltage lockout (UVLO)
circuit with a glitch filter resets the ADM1172 when the supply voltage drops below the specified UVLO limit.
Rev. A | Page 5 of 16

6 Page









ADM1172 pdf, datenblatt
Data Sheet
0.25
0.20
0.15
0.10
VCC = 3V
VCC = 12V
VCC = 15V
VCC = 5V
0.05
0
–50 0
I = 300µA
50 100 150
TEMPERATURE (°C)
Figure 34. PFO Output Low Voltage vs. Temperature, I = 300 μA
0.50
0.45
0.40
0.35
VCC = 3V
0.30
0.25
VCC = 12V
VCC = 5V
0.20
0.15
0.10
VCC = 15V
0.05
0
–50
0
I = 500µA
50 100 150
TEMPERATURE (°C)
Figure 35. PFO Output Low Voltage vs. Temperature, I = 500 μA
ADM1172
0.14
0.12
0.10
0.08
0.06
VCC = 3V
VCC = 15V
0.04
0.02
0
–50
VCC = 12V
VCC = 5V
I = 100µA
0 50 100
TEMPERATURE (°C)
150
Figure 36. PFO Output Low Voltage vs. Temperature, I = 100 μA
700
600 VCC = 3V
500 VCC = 12V
400 VCC = 15V
300 VCC = 5V
200
100
0
–0.1
0.1
0.3
0.5
0.7
0.9
ILOAD (mA)
Figure 37. PFO Output Low Voltage vs. Load Current
1.1
Rev. A | Page 11 of 16

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