Datasheet

LTC2974
37
2974fc
For more information www.linear.com/LTC2974
Figure 18. Control Pin Tracking All Supplies Up And Down
Figure 19. Fault on Channel 1 Tracking All Supplies Down
Tracking Supplies On and Off
The LTC2974 supports tracking power supplies that are equipped with a tracking pin and configured for tracking.
A tracking power supply uses a secondary feedback terminal (TRACK) to allow its output voltage to be scaled to an
external master voltage. T
ypically the external voltage is generated by the supply with the highest voltage in the sys-
tem, which is fed to the slave track pins (see Figure 17). Supplies that track a master supply must be enabled before
the master supply comes up and disabled after the master supply comes down. Enabling the slave supplies when the
master is down requires super
visors monitoring the slaves to disable UV detection. Slave UC detection must also be
pMbus coMManD DescripTion
V
OUT2
V
OUT3
VOUT_EN(3:1)
2974 F19
VOUT_EN0
FAULTB0
CONTROL
UV FAULT ON CHANNEL 1 BRINGS DOWN MASTER
VIA FAULTB0. ALL SLAVE CHANNELS INCLUDING
THE ONE WITH THE UV FAULT ENTER TOFF_DELAY
SLAVE OUTPUT ENABLES TURN ON FIRST SLAVE OUTPUT ENABLES TURN OFF LAST
MASTER BRINGS DOWN
NEXT HIGHEST SLAVE
TON_RISE EXPIRES
FOR ALL CHANNELS.
UV AND UC DETECT ENABLED
ON ALL CHANNELS
TOFF_DELAY ENTERED
FOR ALL CHANNELS.
UV AND UC DETECT DISABLED
ON ALL CHANNELS
V
OUT1
V
OUT0
V
OUT2
V
OUT3
VOUT_EN(3:1)
2974 F18
VOUT_EN0
CONTROL
SLAVE OUTPUT ENABLES TURN ON FIRST SLAVE OUTPUT ENABLES TURN OFF LAST
MASTER BRINGS DOWN
NEXT HIGHEST SLAVE
TON_RISE EXPIRES
FOR ALL CHANNELS.
UV AND UC DETECT ENABLED
ON ALL CHANNELS
TOFF_DELAY ENTERED
FOR ALL CHANNELS.
UV AND UC DETECT DISABLED
ON ALL CHANNELS
V
OUT1
V
OUT0