ANALOG DEVICES ADM1178 Service Manual

V

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Hot Swap Controller and

Digital Power Monitor with ALERTB Output

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

2

C® fast mode-compliant interface (400 kHz maximum)

I
10-lead MSOP

APPLICATIONS

Power monitoring/power budgeting
Central office equipment
Telecommunication and data communication 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

An internal current sense amplifier senses voltage across the sense
resistor in the power path via the VCC pin and the SENSE pin.

2

C interface.

VCC

SENSE

ON

3.15V TO 16.5

ADM1178

FUNCTIONAL BLOCK DIAGRAM

ADM1178

MUX

V

A

CURRENT

SENSE

AMPLIFIER

1.3V
UV COMPARATOR

GND

R

ADM1178

ON

TIMER

Figure 2. Applications Diagram

SENSE

GND

0

I

1

SENSEVCC

GATE

ALERTB

12-BIT

ADC

ALERT

FET DRIVE

CONTROLLER

TIMER

Figure 1.

N-CHANNEL FET

SDA

SCL

ADR

CONTROLLER

SDA
SCL

INTERRUPT

2

C

I

P = VI

SDA
SCL
ADR

ALERTB

GATE

06048-001

06048-002

The ADM1178 limits the current through this resistor by control­ling 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 ADM1178 protects the external FET by limiting the time
that it spends with the maximum current running in 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 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.

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Anal og Devices for its use, nor for any infringements of p atents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.

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.

2

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

2

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

2

C addresses can be

created, depending on the way the ADR pin is connected.

The ADM1178 is packaged in a 10-lead MSOP.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2006 Analog Devices, Inc. All rights reserved.

ADM1178

TABLE OF CONTENTS

Features .............................................................................................. 1

Initial Timing Cycle ................................................................... 14

Applications....................................................................................... 1

General Description......................................................................... 1

Functional Block Diagram .............................................................. 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

Absolute Maximum Ratings............................................................ 6

ESD Caution.................................................................................. 6

Pin Configuration and Function Descriptions............................. 7

Typical Performance Characteristics ............................................. 8

Overview of the Hot Swap Function............................................ 13

Undervoltage Lockout ............................................................... 13

ON Function ............................................................................... 13

TIMER Function ........................................................................ 13

GATE and TIMER Functions During a Hot Swap ............... 14

Calculating Current Limits and Fault Current Limit Time.. 14

Hot Swap Retry Cycle on the ADM1178-1............................. 15

Voltage and Current Readback..................................................... 16

Serial Bus Interface..................................................................... 16

Identifying the ADM1178 on the I

General I

Write and Read Operations ...................................................... 18

Quick Command........................................................................ 18

Write Command Byte................................................................ 18

Write Extended Byte .................................................................. 19

Read Voltage and/or Current Data Bytes................................ 20

Applications Waveforms................................................................ 22

ALERTB Output......................................................................... 23

Kelvin Sense Resistor Connection ........................................... 23

Outline Dimensions ....................................................................... 24

Ordering Guide .......................................................................... 24

2

C Timing.................................................................... 16

2

C Bus............................... 16

REVISION HISTORY

9/06—Revision 0: Initial Version

Rev. 0 | Page 2 of 24

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.

Parameter Min Typ Max Unit Conditions

VCC PIN

Operating Voltage Range, V
Supply Current, I

CC

Undervoltage Lockout, V
Undervoltage Lockout Hysteresis, V

VCC

UVLO

UVLOHYST

ON PIN

Input Current, I

INON

−2 +2 μA
Rising Threshold, V
Trip Threshold Hysteresis, V

ONTH

ONHYST

Glitch Filter Time 3 μs

ALERTB PIN

Output Low Voltage, V

ALERTOL

1 1.5 mA I
Input Current, I

ALERT

SENSE PIN

Input Leakage, I
Overcurrent Fault Timing Threshold, V

Overcurrent Limit Threshold, V

Fast Overcurrent Trip Threshold, V

SENSE

OCTIM

LIM

OCFAST

GATE PIN

Drive Voltage, V

GATE

Pull-Up Current 8 12.5 17 μA V
Pull-Down Current 1.5 mA V
5 mA V
7 mA V

TIMER PIN

Pull-Up Current (Power On Reset), I
Pull-Up Current (Fault Mode), I
Pull-Down Current (Retry Mode), I

Pull-Down Current, I
Trip Threshold H igh, V
Trip Threshold Low, V

100 μA Normal operation, V

TIMERDN

TIMERH

TIMERL

TIMERUPPOR

TIMERUPFAULT

TIMERDNRETRY

ADR PIN

Set Address to 00, V
Set Address to 01, R

Set Address to 10, I

Set Address to 11, V
Input Current for 11 Decode, I
Input Current for 00 Decode, I

ADRLOWV

ADRLOWZ

ADRHIGHZ

ADRHIGHV

ADRLOW

ADRHIGH

3.15 16.5 V

1.7 2.5 mA

2.8 V VCC rising
80 mV

−100

+100 nA ON < 1.5 V

1.26 1.3 1.34 V ON rising
35 50 65 mV

0.05 0.1 V I

−1 +1 μA V

−1 +1 μA V
92 mV

= −100 μA

ALERT

= −2 mA

ALERT

= VCC; ALERTB not asserted

ALERT

= V

SENSE

VCC

V

= (V

OCTRIM

VCC

− V

SENSE

TIMER pin

97 100 103 mV

V

= (V

− V

LIM

VCC

), closed-loop regulation to a

SENSE

current limit

115 mV

V

OCFAST

= (V

VCC

− V

SENSE

turned on

3 6 9 V V
9 11 13 V V
7 10 13 V V

−3.5 −5 −6.5 μA Initial cycle, V

GATE

GATE

GATE

GATE

GATE

GATE

GATE

− V

VCC

− V

VCC

− V

VCC

= 0 V
= 3 V, V
= 3 V, V
= 3 V, V

, V
, V
, V

VCC

VCC

VCC

VCC

VCC

VCC

TIMER

= 3.15 V
= 5 V
= 16.5 V

= 3.15 V
= 5 V
= 16.5 V

= 1 V

−40 −60 −80 μA During current fault, V
2 3 μA

After current fault and during a cool-down
period on a retry device, V

1.26 1.3 1.34 V TIMER rising

0.175 0.2 0.225 V TIMER falling

0 0.8 V Low state
135 150 165 kΩ

Resistor to ground state, load pin with specified
resistance for 01 decode

−1 +1 μA

Open state, maximum load allowed on ADR pin

for 10 decode
2 5.5 V High state
3 10 μA V

−40 −22 μA V

= 2.0 V to 5.5 V

ADR

= 0 V to 0.8 V

ADR

), fault timing starts on the

), gate pull-down current

= 1 V

TIMER

= 1 V

TIMER

= 1 V

TIMER

Rev. 0 | Page 3 of 24

ADM1178

Parameter Min Typ Max Unit Conditions

MONITORING ACCURACY1

Current Sense Absolute Accuracy −1.45

−1.8

−2.8

−5.7

−1.5

−1.8

−2.95

−6.1

−1.95

−2.45

−3.85

−6.7

V

for ADC Full Scale 105.84 mV

SENSE

Voltage Sense Accuracy −0.85

−0.9 +0.9 %

−0.85

−0.9 +0.9 %

−0.9

−1.15 +1.15 %

VCC for ADC Full Scale,

6.65 V
Low Range (VRANGE = 1)
VCC for ADC Full Scale,

26.35 V
High Range (VRANGE = 0)

I2C TIMING

Low Level Input Voltage, V
High Level Input Voltage, V
Low Level Output Voltage on SDA, V
Output Fall Time on SDA from V

Maximum Width of Spikes Suppressed by
Input Filtering on SDA and SCL Pins

Input Current, II, on SDA/SCL When Not
Driving Out a Logic Low

0.3 V

IL

0.7 V

IH

0.4 V I

OL

to V

IHMIN

ILMAX

V

BUS

20 +

0.1 C

250 ns CB = bus capacitance from SDA to GND

B

50 250 ns

−10 +10 μA

Input Capacitance on SDA/SCL 5 pF

SCL Clock Frequency, f

400 kHz

SCL

Low Period of the SCL Clock 600 ns
High Period of the SCL Clock 1300 ns

+1.45 % V

+1.8 % V

+2.8 % V

+5.7 % V

+1.5 % V

+1.8 % V

+2.95 % V

+6.1 % V

+1.95 % V

+2.45 % V

+3.85 % V

+6.7 % V

+0.85 %

+0.85 %

+0.9 %

V

BUS

= 75 mV 0°C to +70°C

SENSE

= 50 mV 0°C to +70°C

SENSE

= 25 mV 0°C to +70°C

SENSE

= 12.5 mV 0°C to +70°C

SENSE

= 75 mV 0°C to +85°C

SENSE

= 50 mV 0°C to +85°C

SENSE

= 25 mV 0°C to +85°C

SENSE

= 12.5 mV 0°C to +85°C

SENSE

= 75 mV −40°C to +85°C

SENSE

= 50 mV −40°C to +85°C

SENSE

= 25 mV −40°C to +85°C

SENSE

= 12.5 mV −40°C to +85°C

SENSE

This is an absolute value to be used when
converting ADC codes to current readings;
any inaccuracy in this value is factored into
absolute current accuracy values (see specs
for Current Sense Absolute Accuracy)

VCC = 3 V minimum

0°C to +70°C

(low range)

= 6 V minimum

V

CC

0°C to +70°C

(high range)
VCC = 3 V minimum

0°C to +85°C

(low range)

= 6 V minimum

V

CC

0°C to +85°C

(high range)
VCC = 3 V minimum

−40°C to +85°C

(low range)

= 6 V minimum

V

CC

−40°C to +85°C

(high range)
These are absolute values to be used when

converting ADC codes to voltage readings;
any inaccuracy in these values is factored into
voltage accuracy values (see specs for Voltage
Accuracy)

= 3 mA

OL

Rev. 0 | Page 4 of 24

ADM1178

Parameter Min Typ Max Unit Conditions

Setup Time for a Repeated Start Condition,
t

SU;STA

SDA Output Data Hold Time, t
Setup Time for a Stop Condition, t

HD;DAT

SU;STO

Bus Free Time Between a Stop and a Start
Condition, t

BUF

Capacitive Load for Each Bus Line 400 pF

1

Monitoring accuracy is a measure of the error in a code that is read back for a particular voltage/current. This is a combination of amplifier error, reference error, ADC

error, and error in ADC full-scale code conversion factor.

600 ns

100 900 ns
600 ns
1300 ns

Rev. 0 | Page 5 of 24

ADM1178

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

VCC Pin 20 V
SENSE Pin 20 V
TIMER Pin −0.3 V to +6 V
ON Pin −0.3 V to +20 V
ALERTB Pin 30 V
GATE Pin 30 V
SDA Pin, SCL Pin −0.3 V to +6 V
ADR Pin −0.3 V to +7 V
Storage Temperature Range −65°C to +125°C
Operating Temperature Range −40°C to +85°C
Lead Temperature Range (Soldering, 10 sec) 300°C
Junction Temperature 150°C

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

Table 3. Thermal Resistance

Package Type θ

10-Lead MSOP 137.5 °C/W

JA

Unit

ESD CAUTION

Rev. 0 | Page 6 of 24

ADM1178

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

1

VCC

SENSE

2

ADM1178

ON

3

TOP VIEW

(Not to Scale)

GND

4
5

TIMER

Figure 3. Pin Configuration

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1 VCC

Positive Supply Input Pin. The operating supply voltage range is from 3.15 V to 16.5 V. An undervoltage
lockout (UVLO) circuit resets the ADM1178 when a low supply voltage is detected.

2 SENSE

Current Sense Input Pin. A sense resistor between the VCC pin and the SENSE pin sets the analog current
limit. The hot swap operation of the ADM1178 controls the external FET gate to maintain the (V
voltage at 100 mV or below.

3 ON

Undervoltage Input Pin. Active high pin. An internal ON comparator has a trip threshold of 1.3 V, and the
output of this comparator is used as an enable for the hot swap operation. With an external resistor divider
from VCC to GND, this pin can be used to enable the hot swap operation on a specific voltage on VCC, giving

an undervoltage function.
4 GND Chip Ground Pin.
5 TIMER

Timer Pin. An external capacitor, C

TIMER

The GATE pin turns off when the TIMER pin is pulled beyond the upper threshold. An overvoltage detection

with an external Zener can be used to force this pin high.
6 SCL I2C Clock Pin. Open-drain input requires an external resistive pull-up.
7 SDA I2C Data I/O Pin. Open-drain input/output. Requires an external resistive pull-up.
8 ADR

9 GATE

2

C Address Pin. This pin can be tied low, tied high, left floating, or tied low through a resistor to set four

I

different I

2

C addresses.

GATE Output Pin. This pin is the high-side gate drive of an external N-channel FET. This pin is driven by the

FET drive controller, which utilizes a charge pump to provide a 12.5 μA pull-up current to charge the FET

GATE pin. The FET drive controller regulates to a maximum load current (100 mV through the sense resistor)

by modulating the GATE pin.
10 ALERTB

Alert Output Pin. Active-low, open-drain configuration. This pin asserts when an overcurrent condition is

present. The overcurrent level that causes an alert to be asserted is digitally programmable via the I

interface. This function can also be enable/disabled via I

10

ALERTB
GATE

9

ADR

8

SDA

7
6

SCL

06048-003

− V

SENSE

)

VCC

, sets a 270 ms/μF initial timing cycle delay and a 21.7 ms/μF fault delay.

2

2

C.

C

Rev. 0 | Page 7 of 24

ADM1178

TYPICAL PERFORMANCE CHARACTERISTICS

2.0

1.8

1.6

1.4

1.2

1.0

(mA)

CC

I

0.8

0.6

0.4

0.2

0

024681014112 16

VCC (V)

Figure 4. Supply Current vs. Supply Voltage

8

06048-021

2.0

1.8

1.6

1.4

1.2

1.0

(mA)

CC

I

0.8

0.6

0.4

0.2

0

–40 806040200–20

TEMPERATURE (°C)

Figure 7. Supply Current vs. Temperature (Gate On)

06048-022

12

10

8

6

DRIVE VOLTAGE (V)

4

2

0

01

Figure 5. Drive Voltage (V

0

–2

–4

–6

(µA)

–8

GATE

I

–10

VCC (V)

− VCC) vs. Supply Voltage

GATE

8161412108642

06048-029

12

10

8

6

DRIVE VOLTAGE (V)

4

2

0

–40 806040200–20

Figure 8. Drive Voltage (V

0

–2

–4

–6

(µA)

–8

GATE

I

–10

5V VIN

3.15V VIN

TEMPERATURE (°C)

− VCC) vs. Temperature

GATE

06048-030

–12

–14

01

VCC (V)

10 12 16148642

8

06048-027

Figure 6. Gate Pull-Up Current vs. Supply Voltage

–12

–14

–40 806040200–20

Figure 9. Gate Pull-Up Current vs. Temperature

Rev. 0 | Page 8 of 24

TEMPERATURE (°C)

06048-028