The ADM1177 is an integrated hot swap controller that offers digital current and voltage monitoring via an on-chip, 12-bit analog-to-digital converter (ADC), communicated through an I2C interface.
An internal current sense amplifier senses voltage across the sense resistor in the power path via the VCC pin and the SENSE pin.
The ADM1177 limits the current through this resistor by control-ling the gate voltage of an external N-channel FET in the power path, via the GATE pin. The sense voltage (and, therefore, the inrush current) is kept below a preset maximum.
The ADM1177 protects the external FET by limiting the time that it spends with maximum current running through it. This current limit period is set by the choice of capacitor attached to the TIMER pin. Additionally, the device provides protection from overcurrent events that may occur once the hot swap event is complete. In the case of a short-circuit event, the current in the sense resistor exceeds an overcurrent trip threshold, and the FET is switched off immediately by pulling down the GATE pin.
A soft start (SS) pin is also included. This gives the user control over the reference on the current sense amplifier. An internal current source charges a capacitor on this pin at startup, allowing the user to set the profile of the initial current ramp. A voltage can also be driven on this pin to alter the reference.
A 12-bit ADC can measure the current seen in the sense resistor, as well as the supply voltage on the VCC pin. An industry-standard I2C interface allows a controller to read current and voltage data from the ADC. Measurements can be initiated by an I2C command. Alternatively, the ADC can run continuously, and the user can read the latest conversion data whenever it is required. Up to four unique I2C addresses can be created, depending on the way the ADR pin is connected.
The ADM1177 is packaged in a 10-lead MSOP.
**Applications**
Power monitoring/power budgeting
Central office equipment
Telecommunication and data communication equipment
PCs/servers
### Features and Benefits
Allows safe board insertion and removal from a live backplane
Controls supply voltages from 3.15 V to 16.5 V
Precision current sense amplifier
Precision voltage input
12-bit ADC for current and voltage readback
Charge pumped gate drive for external N-channel FET
Active high ON pin
10-lead MSOP
Adjustable analog current limit with circuit breaker
±3% accurate hot swap current limit level
Fast response limits peak fault current
Automatic retry or latch-off on current fault
Programmable hot swap timing via TIMER pin
Soft start pin for reference adjustment and programming of initial current ramp rate
I2C fast mode-compliant interface (400 kHz maximum)
