Datasheet
LTC2977
13
2977fa
For more information www.linear.com/LTC2977
PIN FUNCTIONS
PIN NAME PIN NUMBER PIN TYPE DESCRIPTION
V
SENSEM6
1* In DC/DC Converter Differential (–) Output Voltage-6 Sensing Pin
V
SENSEP7
2* In DC/DC Converter Differential (+) Output Voltage or Current-7 Sensing Pin
V
SENSEM7
3* In DC/DC Converter Differential (–) Output Voltage or Current-7 Sensing Pin
V
OUT_EN0
4 Out DC/DC Converter Enable-0 Pin. Output High Voltage Optionally Pulled Up to 12V by 5µA
V
OUT_EN1
5 Out DC/DC Converter Enable-1 Pin. Output High Voltage Optionally Pulled Up to 12V by 5µA
V
OUT_EN2
6 Out DC/DC Converter Enable-2 Pin. Output High Voltage Optionally Pulled Up to 12V by 5µA
V
OUT_EN3
7 Out DC/DC Converter Enable-3 Pin. Output High Voltage Optionally Pulled Up to 12V by 5µA
V
OUT_EN4
8 Out DC/DC Converter Open-Drain Pull-Down Output-4
V
OUT_EN5
9 Out DC/DC Converter Open-Drain Pull-Down Output-5
V
OUT_EN6
10 Out DC/DC Converter Open-Drain Pull-Down Output-6
V
OUT_EN7
11 Out DC/DC Converter Open-Drain Pull-Down Output-7
V
IN_EN
12 0ut DC/DC Converter V
IN
ENABLE Pin. Output High Voltage Optionally Pulled Up to 12V by 5µA
DNC 13 Do Not Connect Do Not Connect to This Pin
V
IN_SNS
14 In V
IN
SENSE Input. This Voltage is Compared Against the V
IN
On and Off Voltage Thresholds in Order to
Determine When to Enable and Disable, Respectively, the Downstream DC/DC Converters.
V
PWR
15 In V
PWR
Serves as the Unregulated Power Supply Input to the Chip (4.5V to 15V). If a 4.5V to 15V Supply
Voltage is Unavailable, Short V
PWR
to V
DD33
and Power the Chip Directly from a 3.3V Supply. Bypass to
GND with 0.1µF Capacitor.
V
DD33
16 In/Out If Shorted to V
PWR
, it Serves as 3.13V to 3.47V Supply Input Pin. Otherwise, it is a 3.3V Internally
Regulated Voltage Output (Use 0.1µF Decoupling Capacitor to GND).
V
DD33
17 In Input for Internal 2.5V Sub-Regulator. Short This Pin to Pin 16.
V
DD25
18 In/Out 2.5V Internally Regulated Voltage Output. Bypass to GND with a 0.1µF Capacitor.
WP 19 In Digital Input. Write-Protect Input Pin, Active High.
PWRGD 20 Out Power Good Open-Drain Output. Indicates When Outputs are Power Good. Can be Used as System
Power-On Reset.
SHARE_CLK
21 In/Out Bidirectional Clock Sharing Pin. Connect a 5.49k Pull-Up Resistor to V
DD33
.
WDI/RESETB 22 In Watchdog Timer Interrupt and Chip Reset Input. Connect a 10k Pull-Up Resistor to V
DD33
. Rising Edge
Resets Watchdog Counter. Holding This Pin Low for More Than t
RESETB
Resets the Chip.
FAULTB00 23 In/Out Open-Drain Output and Digital Input. Active Low Bidirectional Fault Indicator-00. Connect a 10k Pull-Up
Resistor to V
DD33
.
FAULTB01 24 In/Out Open-Drain Output and Digital Input. Active Low Bidirectional Fault Indicator-01. Connect a 10k Pull-Up
Resistor to V
DD33
.
FAULTB10 25 In/Out Open-Drain Output and Digital Input. Active Low Bidirectional Fault Indicator-10. Connect a 10k Pull-Up
Resistor to V
DD33
.
FAULTB11 26 In/Out Open-Drain Output and Digital Input. Active Low Bidirectional Fault Indicator-11. Connect a 10k Pull-Up
Resistor to V
DD33
.
SDA 27 In/Out PMBus Bidirectional Serial Data Pin
SCL 28 In PMBus Serial Clock Input Pin (400kHz Maximum)
ALERTB 29 Out Open-Drain Output. Generates an Interrupt Request in a Fault/Warning Situation.
CONTROL0 30 In Control Pin 0 Input
CONTROL1 31 In Control Pin 1 Input
ASEL0 32 In Ternary Address Select Pin 0 Input. Connect to V
DD33
, GND or Float to Encode 1 of 3 Logic States.
ASEL1 33 In Ternary Address Select Pin 1 Input. Connect to V
DD33
, GND or Float to Encode 1 of 3 Logic States.
REFP 34 Out Reference Voltage Output. Needs 0.1µF Decoupling Capacitor to REFM.
REFM 35 Out Reference Return Pin. Needs 0.1µF Decoupling Capacitor to REFP.
V
SENSEP0
36* In DC/DC Converter Differential (+) Output Voltage-0 Sensing Pin
V
SENSEM0
37* In DC/DC Converter Differential (–) Output Voltage-0 Sensing Pin
V
DACM0
38 Out DAC0 Return. Connect to Channel 0 DC/DC Converter’s GND Sense or Return to GND.
V
DACP0
39 Out DAC0 Output
V
DACP1
40 Out DAC1 Output