Datasheet

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Hot Swap Controller and

Digital Power Monitor with ALERTB Output

Data Sheet

ADM1178

Rev. D

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FEATURES

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

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

Active high ON pin

ALERTB output for overcurrent interrupt

C fast mode-compliant interface (400 kHz maximum)

10-lead MSOP

APPLICATIONS

Power monitoring/power budgeting

Central office equipment

Telecommunications and data communications equipment

PCs/servers

GENERAL DESCRIPTION

The ADM1178 is an integrated hot swap controller and current

sense amplifier that offers digital current and voltage monitoring

via an on-chip 12-bit analog-to-digital converter (ADC),

communicated through an I

C® interface.

An internal current sense amplifier measures voltage across the

sense resistor in the power path via the VCC pin and the SENSE pin.

The ADM1178 limits the current through this resistor by control-

ling the gate voltage (via the GATE pin) of an external N-channel

FET in the power path. The voltage across the sense resistor (and

therefore the inrush current) is kept below a preset maximum.

The ADM1178 protects the external FET by limiting the time that

the maximum current runs through it. This current limit period

is set by the value of the capacitor attached to the TIMER pin.

Additionally, the device provides protection from overcurrent

events that may occur after the hot swap event is complete. In

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.

FUNCTIONAL BLOCK DIAGRAM

ADM1178

SENSE

VCC

1.3V

MUX

12-BIT

ADC

FET DRIVE

CONTROLLER

GND

CURRENT

SENSE

AMPLIFIER

UNDERVOLTAGE

COMPARATOR

SDA

SCL

ADR

ALERTB

GATE

TIMER

ALERT

06048-001

Figure 1.

SENSE

N-CHANNEL FET

P = VI

CONTROLLER

ADM1178

SENSEVCC

SDA

SCL

SDA

SCL

GND

GATE

INTERRUPT

ALERTB

ADR

TIMER

3.15V TO 16.5V

06048-002

Figure 2. Applications Diagram

A 12-bit ADC can measure the current seen in the sense

resistor, as well as the supply voltage on the VCC pin. An alert

output can be set to trigger when the ADC current reading

exceeds a programmed overcurrent limit threshold.

An industry-standard I

C interface allows a controller to read

current and voltage data from the ADC. Measurements can be

initiated by an I

C command. Alternatively, the ADC can run

continuously, and the user can read the latest conversion data

whenever it is required. Up to four unique I

C addresses can be

created, depending on how the ADR pin is connected.

The ADM1178 is packaged in a 10-lead MSOP.

Summary of content (24 pages)

PAGE 1
FEATURES APPLICATIONS Power monitoring/power budgeting Central office equipment Telecommunications and data communications equipment PCs/servers GENERAL DESCRIPTION The ADM1178 is an integrated hot swap controller and current sense amplifier that offers digital current and voltage monitoring via an on-chip 12-bit analog-to-digital converter (ADC), communicated through an I2C® interface.
PAGE 2
ADM1178 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Initial Timing Cycle ................................................................... 13 Applications ....................................................................................... 1 Hot Swap Retry Cycle on the ADM1178-1 ............................. 14 General Description .........................................................................
PAGE 3
Data Sheet ADM1178 SPECIFICATIONS VCC = 3.15 V to 16.5 V, TA = −40°C to +85°C, typical values at TA = 25°C, unless otherwise noted. Table 1.
PAGE 4
ADM1178 Parameter MONITORING ACCURACY 1 Current Sense Absolute Accuracy 0°C to +70°C 0°C to +85°C −40°C to +85°C VSENSE for ADC Full Scale 2 Voltage Sense Accuracy 0°C to +70°C 0°C to +85°C −40°C to +85°C VCC for ADC Full Scale 3 Low Range (VRANGE = 1) High Range (VRANGE = 0) 2 I C TIMING Low Level Input Voltage, VIL High Level Input Voltage, VIH Low Level Output Voltage on SDA, VOL Output Fall Time on SDA from VIHMIN to VILMAX Maximum Width of Spikes Suppressed by Input Filtering on SDA and SCL Pins Inp
PAGE 5
Data Sheet ADM1178 ABSOLUTE MAXIMUM RATINGS THERMAL CHARACTERISTICS Table 2. Parameter VCC Pin SENSE Pin TIMER Pin ON Pin ALERTB Pin GATE Pin SDA Pin, SCL Pin ADR Pin Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10 sec) Junction Temperature Rating 20 V 20 V −0.3 V to +6 V −0.3 V to +20 V 30 V 30 V −0.3 V to +6 V −0.
PAGE 6
ADM1178 Data Sheet PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VCC 1 ADM1178 9 GATE ON 3 TOP VIEW (Not to Scale) 8 ADR 7 SDA 6 SCL GND 4 TIMER 5 06048-003 10 ALERTB SENSE 2 Figure 3. Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 Mnemonic VCC 2 SENSE 3 ON 4 5 GND TIMER 6 7 8 SCL SDA ADR 9 GATE 10 ALERTB Description Positive Supply Input Pin. The operating supply voltage range is from 3.15 V to 16.5 V.
PAGE 7
Data Sheet ADM1178 2.0 1.8 1.8 1.6 1.6 1.4 1.4 1.2 1.2 1.0 0.8 1.0 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 2 4 6 8 10 12 14 16 18 VCC (V) 0 –40 10 10 DRIVE VOLTAGE (V) 40 60 80 8 6 4 5V VCC 8 3.15V VCC 6 4 2 2 4 6 8 10 12 14 16 18 VCC (V) 0 –40 06048-029 0 –2 –2 –4 –4 IGATE (µA) 0 –6 –8 –12 –12 10 12 14 16 VCC (V) 18 –14 –40 06048-027 8 60 80 –8 –10 6 40 –6 –10 4 20 Figure 8. Drive Voltage (VGATE − VCC) vs.
PAGE 8
ADM1178 Data Sheet 2.0 12 1.8 10 TIMER THRESHOLD (V) 1.6 6 4 1.4 HIGH 1.2 1.0 0.8 0.6 0.4 2 LOW 0.2 0 2 4 6 8 10 12 14 16 18 VCC (V) 0 06048-031 0 0 2 4 6 8 10 12 14 16 18 VCC (V) Figure 10. Gate Pull-Down Current vs. Supply Voltage at VGATE = 5 V 06048-038 IGATE (mA) 8 Figure 13. Timer Threshold vs. Supply Voltage 2.0 2 1.8 0 1.6 TIMER THRESHOLD (V) –2 IGATE (µA) –4 –6 –8 –10 HIGH 1.4 1.2 1.0 0.8 0.6 0.
PAGE 9
ADM1178 0 –1 –1 –2 –2 –3 –4 –4 –5 –5 2 4 6 8 10 12 14 16 18 VCC (V) –6 –40 –10 –20 –20 –30 –30 ITIMER (µA) –10 –40 –50 –60 –60 –70 –70 4 6 8 10 12 14 16 18 VCC (V) –80 –40 2.5 2.5 2.0 2.0 ITIMER (µA) 3.0 1.5 1.0 0.5 0.5 6 8 10 VCC (V) 12 14 16 18 0 –40 06048-036 4 –20 0 20 40 60 80 1.5 1.0 2 80 Figure 20. Timer Pull-Up Current (Circuit Breaker Delay) vs. Temperature 3.0 0 60 TEMPERATURE (°C) Figure 17.
PAGE 10
ADM1178 Data Sheet 1000 120 900 HITS PER CODE (1000 READS) 115 110 100 95 90 85 4 6 8 10 12 14 16 18 Figure 22. Circuit Breaker Limit Voltage vs. Supply Voltage 400 300 200 0 2046 2047 2048 2049 2050 CODE Figure 25.
PAGE 11
Data Sheet ADM1178 1.0 4 3 ALERTB OUTPUT LOW (V) 0.8 2 INL (LSB) 1 0 –1 –2 0.6 0.4 0.2 0 500 1000 1500 2000 2500 3000 3500 4000 CODE 0 06048-023 –4 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 VCC (V) 06048-048 –3 Figure 31. ALERTB Output Low Voltage vs. Supply @ 1 mA Figure 28. INL for ADC 2.0 4 1.8 3 ALERTB OUTPUT LOW (V) 1.6 1 0 –1 1.4 1.2 1.0 0.8 0.6 0.4 –2 0.2 –3 0 500 1000 1500 2000 2500 3000 3500 4000 CODE 06048-024 0 –4 0.60 0.55 0.45 0.40 0.
PAGE 12
ADM1178 Data Sheet OVERVIEW OF THE HOT SWAP FUNCTION When circuit boards are inserted into a live backplane, discharged supply bypass capacitors draw large transient currents from the backplane power bus as they charge. Such transient currents can cause permanent damage to connector pins, as well as dips on the backplane supply that can reset other boards in the system.
PAGE 13
Data Sheet ADM1178 GATE AND TIMER FUNCTIONS DURING A HOT SWAP OPERATION CALCULATING CURRENT LIMITS AND FAULT CURRENT LIMIT TIME During hot insertion of a board onto a live supply rail at VCC, the abrupt application of supply voltage charges the external FET drain/gate capacitance, which can cause an unwanted gate voltage spike. An internal circuit holds GATE low before the internal circuitry wakes up. This substantially reduces the FET current surges at insertion.
PAGE 14
ADM1178 Data Sheet When the initial timing cycle terminates, the device is ready to start a hot swap operation (assuming that the ON pin is asserted). In the example shown in Figure 33, the ON pin is asserted at the same time as VCC is applied; therefore, the hot swap operation starts immediately after Time Point 4. At this point, the FET gate is charged up with a 12.5 µA current source.
PAGE 15
Data Sheet ADM1178 VOLTAGE AND CURRENT READBACK In addition to providing hot swap functionality, the ADM1178 contains the components to allow voltage and current readback over an I2C bus. The voltage output of the current sense amplifier and the voltage on the VCC pin are fed into a 12-bit ADC via a multiplexer. The device can be instructed to convert voltage and/or current at any time during operation via an I2C command.
PAGE 16
ADM1178 Data Sheet 9 1 9 1 SCL 1 SDA 1 1 1 ADRA ADRB 0 D7 R/W D6 D5 ACKNOWLEDGE BY SLAVE START BY MASTER FRAME 1 SLAVE ADDRESS 1 D4 D2 D3 D0 D1 ACKNOWLEDGE BY SLAVE FRAME 2 COMMAND CODE 1 9 9 SCL (CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 ACKNOWLEDGE BY SLAVE FRAME 3 DATA BYTE D3 D2 D1 D0 ACKNOWLEDGE BY STOP BY SLAVE MASTER FRAME N DATA BYTE 06048-006 SDA (CONTINUED) Figure 35.
PAGE 17
Data Sheet ADM1178 WRITE AND READ OPERATIONS Table 6. I2C Abbreviations Abbreviation S P R W A N Condition Start Stop Read Write Acknowledge No acknowledge WRITE COMMAND BYTE In the write command byte operation, the master device sends a command byte to the slave device, as follows: 1. 2. 3. 4. 5. 6. QUICK COMMAND 1 The quick command operation allows the master to check if the slave is present on the bus, as follows: 3. 4. The master device asserts a start condition on SDA.
PAGE 18
ADM1178 Data Sheet WRITE EXTENDED COMMAND BYTE 1. 2. 3. 4. 5. 6. The master device asserts a start condition on SDA. The master sends the 7-bit slave address, followed by the write bit (low). The addressed slave device asserts an acknowledge on SDA. The master sends the register address byte. The MSB of this byte is set to 1 to indicate an extended register write. The two LSBs indicate which of the three extended registers is written to (see Table 8). All other bits should be set to 0.
PAGE 19
Data Sheet ADM1178 2 3 4 1 The ADM1178 digitizes both voltage and current. Three bytes are read back in the format shown in Table 12. SLAVE S R A ADDRESS Byte 1 2 3 Contents Voltage MSBs Voltage MSBs Voltage LSBs B7 V11 I11 V3 B6 V10 I10 V2 B5 V9 I9 V1 B4 V8 I8 V0 B3 V7 I7 I3 B2 V6 I6 I2 B1 V5 I5 I1 B0 V4 I4 I0 Voltage Readback The ADM1178 digitizes voltage only. Two bytes are read back in the format shown in Table 13. Table 13.
PAGE 20
ADM1178 Data Sheet Table 15. Status Byte Operations Bit 0 1 2 Name ADC_OC ADC_ALERT HS_OC 3 4 HS_ALERT OFF_STATUS 5 OFF_ALERT Function An ADC-based overcurrent comparison is detected on the last three conversions. An ADC-based overcurrent trip has occurred, causing the alert. Cleared by writing to Bit 4 of the ALERT_EN register. The hot swap operation is off due to an analog overcurrent event. On parts that latch off, this is the same as the HS_ALERT status bit (if EN_HS_ALERT = 1).
PAGE 21
Data Sheet ADM1178 APPLICATIONS INFORMATION APPLICATIONS WAVEFORMS 1 1 2 2 3 3 4 CH2 1.00V CH4 10.0V M40.0ms CH1 1.5A CH3 20.0V Figure 44. Inrush Current Control into 220 µF Load (Channel 1 = ILOAD, Channel 2 = VTIMER, Channel 3 = VGATE, Channel 4 = VOUT) CH2 1.00V CH4 10.0V M10.0ms 06048-073 CH1 1.5A CH3 20.0V 06048-070 4 Figure 47.
PAGE 22
ADM1178 Data Sheet ALERTB OUTPUT KELVIN SENSE RESISTOR CONNECTION The ALERTB output is an open-drain pin with 30 V tolerance. This output can be used as an overcurrent flag by connecting it to the general-purpose logic input of a controller. During normal operation, this output is pulled high. (An external pull-up resistor should be used because this is an open-drain pin.) When an overcurrent condition occurs, the ADM1178 pulls this output low.
PAGE 23
Data Sheet ADM1178 OUTLINE DIMENSIONS 3.10 3.00 2.90 10 3.10 3.00 2.90 5.15 4.90 4.65 6 1 5 PIN 1 IDENTIFIER 0.50 BSC 0.95 0.85 0.75 15° MAX 1.10 MAX 0.30 0.15 6° 0° 0.23 0.13 COMPLIANT TO JEDEC STANDARDS MO-187-BA 0.70 0.55 0.40 091709-A 0.15 0.05 COPLANARITY 0.10 Figure 50.
PAGE 24
ADM1178 Data Sheet NOTES I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors). ©2006–2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06048-0-6/12(D) Rev.