Datasheet

LTC2974
13
2974fc
For more information www.linear.com/LTC2974
pin FuncTions
PIN NAME PIN NUMBER PIN TYPE DESCRIPTION
V
SENSEP0
1* In DC/DC Converter Differential (+) Output Voltage-0 Sensing Pin
V
SENSEM0
2* In DC/DC Converter Differential (–) Output Voltage-0 Sensing Pin
V
OUT_EN0
3 Out DC/DC Converter Enable-0 Pin. Output High Voltage Optionally Pulled-Up to 12V by 5µA
V
OUT_EN1
4 Out DC/DC Converter Enable-1 Pin. Output High Voltage Optionally Pulled-Up to 12V by 5µA
V
OUT_EN2
5 Out DC/DC Converter Enable-2 Pin. Output High Voltage Optionally Pulled-Up to 12V by 5µA
V
OUT_EN3
6 Out DC/DC Converter Enable-3 Pin. Output High Voltage Optionally Pulled-Up to 12V by 5µA
AUXFAULTB 7 Out Auxillary Fault Output Pin. Output High Voltage Optionally Pulled-Up to 12V by 5µA. Can Be
Configured to Pull Low When OV/UV/OC/UC Detected
DNC 8 Do Not Connect Do Not Connect to this Pin
V
IN_SNS
9 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
10 In V
PWR
Serves as the Unregulated Power Supply Input to the Chip (4.5 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
11 In/Out If Shorted to V
PWR
, It Serves as 3.13 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
12 In Input for Internal 2.5V Sub-Regulator. Short this Pin to Pin 11
V
DD25
13 In/Out 2.5V Internally Regulated Voltage Output. Bypass to GND with a 0.1µF Capacitor
V
DD25
14 In 2.5V Supply Voltage Input. Short this Pin to Pin 13
T
SENSE0
15* In/Out External Temperature Current Output and Voltage Input for Channel 0. Maximum allowed capacitance
is 1µF
T
SENSE1
16* In/Out External Temperature Current Output and Voltage Input for Channel 1. Maximum allowed capacitance
is 1µF
PWRGD 17 Out Power-Good Open Drain Output. Indicates When Selected Outputs Are Power Good. Can be Used as
System Power-on Reset
SHARE_CLK 18 In/Out Bidirectional Clock Sharing Pin. Connect a 5.49kΩ Pull-Up Resistor to V
DD33
GND 19 Ground Chip Ground. Must Be Soldered to PCB
GND 20 Ground Chip Ground. Must Be Soldered to PCB
GND 21 Ground Chip Ground. Must Be Soldered to PCB
CONTROL2 22 In Control Pin 2 Input
CONTROL3 23 In Control Pin 3 Input
WDI/RESETB 24 In Watchdog Timer Interrupt and Chip Reset Input. Connect a 10kΩ Pull-Up Resistor to V
DD33
. Rising
Edge Resets Watchdog Counter. Holding this Pin Low for More than t
RESETB
Resets the Chip
FAULTB0 25 In/Out Open-Drain Output and Digital Input. Active Low Bidirectional Fault Indicator-0. Connect a 10kΩ
Pull-Up Resistor to V
DD33
FAULTB1 26 In/Out Open-Drain Output and Digital Input. Active Low Bidirectional Fault Indicator-1. Connect a 10kΩ
Pull-Up Resistor to V
DD33
T
SENSE2
27* In/Out External Temperature Current Output and Voltage Input for Channel 2. Maximum allowed capacitance
is 1µF
WP 28 In Digital Input. Write-Protect Input Pin, Active High
SDA 29 In/Out PMBus Bidirectional Serial Data Pin
SCL 30 In PMBus Serial Clock Input Pin (400kHz Maximum)
ALERTB 31 Out Open-Drain Output. Generates an Interrupt Request in a Fault/Warning Situation
CONTROL0 32 In Control Pin 0 Input
CONTROL1 33 In Control Pin 1 Input