Datasheet

LTC2974
85
2974fc
For more information www.linear.com/LTC2974
applicaTions inForMaTion
Figure 29. Typical Connections between Multiple LTC2974s
Figure 30. Aborted On-Sequence Due to Channel 1 Short
VIN_SNS
AUXFAULTB
SDA
SCL
ALERTB
CONTROL0
WDI/RESETB
FAULTB0
SHARE_CLK
PWRGD
GND
LTC2974 #1
VIN_SNS
AUXFAULTB
SDA
SCL
ALERTB
CONTROL0
WDI/RESETB
FAULTB0
SHARE_CLK
PWRGD
GND
2974 F29
LTC2974 #n
TO V
IN
OF
DC/DCs
TO INPUT
SWITCH
TO HOST CONTROLLER
TO OTHER LTC2974s–10k EQUIVALENT PULL-UP RECOMMENDED
ON EACH LINE EXCEPT SHARE_CLK (USE 5.49k)
V
CONTROL
V
OUT0
TON_DELAY0
V
OUT1
V
OUT2
V
OUTn
BUSSED
V
FAULTBn
PINS
TON_MAX_FAULT1
2974 F30
TON_DELAY1
TON_DELAY2
TON_DELAYn
•
•
•
•
•
•
APPLICATION CIRCUITS
Trimming and Margining DC/DC Converters with
External Feedback Resistors
Figure 31 shows a typical application circuit for trimming/
margining a power supply with an external feedback
network. The V
SENSEP0
and V
SENSEM0
differential inputs
sense the load voltage directly, and a correction voltage
is developed on the V
DAC0
pin by the closed-loop servo
algorithm. The V
DAC0
output is connected to the DC/DC
converter’s feedback node through resistor R30. For this
configuration, set Mfr_config_dac_pol to 0.
Four-Step Resistor Selection Procedure for DC/DC
Converters with External Feedback Resistors
The following four-step procedure should be used to
calculate the resistor values required for the application
circuit shown in Figure 31.
1. Assume values for feedback resistor R20 and the nominal
DC/DC converter output voltage V
DC(NOM)
, and solve
for R10.
V
DC(NOM)
is the output voltage of the DC/DC converter
when the LTC2974’s V
DAC0
pin is in a high impedance