LTC2970-1 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2970-1' PDF : 36 Pages View PDF
U
OPERATIO
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.
LTC2970/LTC2970-1
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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