LTC2970CUFD datasheet(13/36 Pages) LINER

13 / 36 page

LTC2970/LTC2970-1

29701fc

1. LTC2970 Operation Overview

The LTC2970 is designed to control and monitor two

power supplies. The LTC2970’s superior accuracy allows

it to precisely servo each supply’s output voltage over a

wide range of operating conditions; increasing accuracy,

reducing power requirements and component costs. Mar-

gining may be performed with equal ease and precision.

The monitoring functions allow for increased reliability

by alerting a system host about incipient failures before

they occur. The seven channel ADC may also be used to

monitor current, temperature, and the 5V or optional 12V

supply.

The LTC2970’s unique architecture and control algorithm

have been especially tailored for power supply manage-

ment. The soft connect feature allows the LTC2970 to begin

controlling a power supply without perturbing its initial

value. The delta-sigma ADC architecture was speciﬁcally

chosen to average out power-supply noise and allow the

LTC2970 to ignore fast transients. Unlike discrete time

DACs, the LTC2970’s continuous time, voltage buffered

IDAC is ideal for noise sensitive applications. The servo

algorithm limits the IDAC step size to one LSB per iteration

in order to minimize power supply transients. The point

of load ground reference for the IDAC outputs minimize

errors that would otherwise occur in a power system that

experiences ground bounce. By selecting two resistor

values, the user can choose the appropriate resolution

while providing an important hardware range limit beyond

which the supply may not be driven. The servo on fault

option allows the LTC2970 to further reduce output voltage

disturbances by only stepping the IDAC when the output

voltage drifts outside of a user programmable window.

The LTC2970 powers up in a high impedance state and

will not interfere with default power supply operation.

Similarly, powering down the LTC2970 will restore its

high impedance state.

OPERATIO

All communication with the LTC2970 is performed over

an industry standard I2C bus. The LTC2970 I2C interface

also meets all SMBus setup times, hold times, and timeout

requirements. The ALERT pin may be used to signal that

one or more of the fourteen conﬁgurable fault limits have

been reached. Each fault may be individually masked. The

I2C interface supports word reads, word writes and the

SMBus Alert Response Address protocol. Two general

purpose IO pins may be used to provide additional fault

information or user deﬁned system control. Powering down

the LTC2970 will not interfere with I2C operation.

The LTC2970-1 enables power supply tracking and se-

quencing with the addition of a few external components.

A special global address and synchronization command

allow multiple LTC2970-1’s to track and sequence multiple

pairs of power supplies.

The LTC2970 can perform the following operations:

• Accept all programming commands and report status

over the I2C or SMBus bus.

• Command each voltage buffered IDAC to connect to the

corresponding power supply’s feedback node through

an external resistor using the IDAC code that most

closely approximates the feedback node’s regulation

voltage (Soft Connect).

• Command each voltage buffered IDAC output to connect

to the corresponding power supply’s feedback node

through an external resistor with a user-selected IDAC

code (Hard Connect).

• Change the code of a previously connected IDAC.

• Disconnect each voltage buffered IDAC output from the

power supply’s feedback node.

• LTC2970-1 Only: Track two power supplies up or down.

Multiple LTC2970-1’s can be conﬁgured to track simul-

taneously or in a sequence.

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