ltc2978 Linear Technology Corporation, ltc2978 Datasheet - Page 50

• Manufacturer Part Number: ltc2978
• Description: Octal Pmbus Power Supply Monitor And Controller With Eeprom
• Manufacturer: Linear Technology Corporation

LTC2978 Overview
The LTC2978 is a power management IC that is capable
of sequencing, margining, trimming, OV/UV supervision,
providing fault management, and voltage read back for
eight DC/DC converters. Input voltage and temperature
read back is also available. Odd numbered channels can be
configured to read back sense resistor voltages. Multiple
LTC2978s can be synchronized to operate in unison using
the SHARE_CLK, FAULTB and CONTROL pins. The LTC2978
utilizes a PMBus compliant interface and command set.
Setting Command Register Values
The command register settings described herein are for
the purpose of understanding and software development
in a host processor. In actual practice, the LTC2978 can
be completely configured for standalone operation with
the LTC DC590B dongle and software GUI using intuitive
menu driven objects.
Command Units On or Off
Three control parameters determine how a particular
channel is turned on and off. The CONTROLn pins, the
OPERATION command and the value of the input voltage
measured at the V
exceed V
below V
will result. Refer to the OPERATION section in the data
sheet for a detailed description of the ON_OFF_CONFIG
command.
LTC2978
applicaTions inForMaTion
0
IN_OFF
IN_ON
, an immediate shutdown of all channels
in order to enable a start. When V
IN_SNS
pin (V
V
CONTROL
V
OUT_EN
V
OUT
IN
). In all cases, V
Figure 11. Typical On Sequence Using Control Pin
VOUT_0V_FAULT_LIMIT
DAC SOFT-CONNECTS
ADJUSTING OUTPUT
TON_DELAY
AND BEGINS
IN
IN
drops
must
Some examples of typical ON/OFF configurations are:
1. A DC/DC may be configured to turn on anytime V
2. A DC/DC may be configured to turn on only when it
3. A DC/DC may be configured to turn on only via the
4. A DC/DC may be configured to turn on only when it
On Sequencing
The TON_DELAY command sets the amount of time that
a channel will wait following the start of an ON sequence
before its V
the DC/DC converter has been enabled, the TON_RISE
command determines the amount of time the LTC2978
waits before the V
DC/DC converter output is servoed to VOUT_COMMAND
volts. The TON_MAX_FAULT_LIMIT command determines
the amount of time after the DC/DC converter has been
enabled that an undervoltage condition will be tolerated
before a fault occurs. If a TON_MAX_FAULT occurs, the
channel can be configured to disable the DC/DC converter
and propagate the fault to other channels using the bidi-
rectional FAULTBzn pins. Figure 11 shows a typical on-
sequence using the CONTROL pin.
TON_RISE
exceeds V
receives an OPERATION command.
CONTROL pin.
receives an OPERATION command and the CONTROL
pin is asserted.
V
DC_NOM
OUT_ENn
VOUT_UV_FAULT_LIMIT
2978 F11
TON_MAX_FAULT_LIMIT
IN_ON
V
OUT_COMMAND
DACPn
.
pin will enable a DC/DC converter. Once
output is soft-connected and the
2978fa
IN