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Linear Technology LTC2977 Demo Board: Octal Power Supply Manager [Requires DC1613] DC2028A DC2028A Data Sheet

Product codes
DC2028A
Download
Page of 94
LTC2977
82
2977fa
For more information 
applicaTions inForMaTion
•   WDI/RESETB can be used to put the LTC2977 in the 
power-on reset state. Pull WDI/RESETB low for at least 
t
RESETB
 to enter this state. 
•   The FAULTBzn lines can be connected together to create 
fault dependencies. Figure 21 shows a configuration 
where a fault on any FAULTBzn will pull all others low. 
This is useful for arrays where it is desired to abort a 
start-up sequence in the event any channel does not 
come up (see Figure 22). 
•   PWRGD  reflects  the  status  of  the  outputs  that  are 
mapped to it by the MFR_PWRGD_EN command. Fig-
ure 20 shows all the PWRGD pins connected together, 
but any combination may be used.
APPLICATION CIRCUITS
Trimming and Margining DC/DC Converters with 
External Feedback Resistors
Figure 23 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  between  the  V
DACP0
  and  V
DACM0
  pins 
by  the  closed-loop  servo  algorithm.  V
DACM0
  is  Kelvin 
connected to the point-of-load GND in order to minimize 
the effects of load induced grounding errors. The V
DACP0
 
output is connected to the DC/DC converter’s feedback 
node  through  resistor  R30.  For  this  configuration,  set 
Mfr_config_dac_pol to 0.
Figure 22. Aborted On Sequence Due to Channel 1 Short
V
CONTROLn
V
OUT0
TON_DELAY0
V
OUT1
V
OUT2
V
OUTn
BUSSED
VFAULTBzn
PINS
TON_MAX_FAULT1
2977 F22
TON_DELAY1
TON_DELAY2
TON_DELAYn
•
•
•
•
•
•
Figure 23. Application Circuit for DC/DC Converters with External Feedback Resistors
V
PWR
V
DD33
V
DD33
V
DD25
V
IN_SNS
V
DACP0
V
SENSEP0
V
DACM0
V
SENSEM0
V
OUT_EN0
LTC2977*
0.1µF
0.1µF
V
IN
4.5V < V
IBUS
 < 15V
GND
*SOME DETAILS OMITTED FOR CLARITY
ONLY ONE OF EIGHT CHANNELS SHOWN
V
IN
V
OUT
R20
R30
R10
2977 F23
RUN/SS
SGND
V
FB
GND
DC/DC
CONVERTER
LOAD
0.1µF