SC403B Datasheet, PDF (13/32 Pages) Semtech Corporation – 6A EcoSpeed® Integrated FET Regulator with Programmable LDO

SC403B
Pin Descriptions
Pin #
1
2
3
4, 30, PAD 1
5
6, 9-11,
PAD 2
7
8
12
Pin Name Pin Function
FB
Feedback input for switching regulator used to program the output voltage — connect to an external resis-
tor divider from VOUT to AGND.
VOUT
Switcher output voltage sense pin — also the input to the internal switch-over between VOUT and VLDO.
The voltage at this pin must be less than or equal to the voltage at the VDD pin.
VDD
Bias supply for the IC — when using the internal LDO as a bias power supply, the VDD is the LDO output.
When using an external power supply to bias the IC, the LDO output should be disabled.
AGND
Analog ground
FBL
Feedback input for the internal LDO — connect to an external resistor divider from VDD to AGND to pro-
gram the LDO output.
VIN
Input supply voltage
SS
The soft start time is programmed by an internal current source charging a capacitor on this pin.
Bootstrap pin — connect a capacitor of at least 100nF from BST to LX to develop the floating supply for the
BST
high-side gate drive.
NC
No connection
13
LXBST
LX Boost — connect to the BST capacitor.
23-25, PAD 3
LX
Switching (phase) node
14
NC
No connection
15-22
26
27
PGND
PGOOD
ILIM
Power ground
Open-drain power good indicator — high impedance indicates power is good. An external pull-up
resistor is required.
Current limit sense pin — used to program the current limit by connecting a resistor from ILIM to LXS.
28
LXS
LX sense — connects to R_ILIM.
Enable/power-save input for the switching regulator — connect to AGND to disable the switching regulator.
29
EN/PSV Float to operate in forced continuous mode (PSAVE disabled). Connect to VDD to operate with PSAVE mode
enabled.
31
TON
On-time programming input — set the on-time by connecting through a resistor to AGND.
Enable input for the LDO — connect ENL to AGND to disable the LDO. Drive with logic signal for logic con-
32
ENL
trol, or program the VIN UVLO with a resistor divider between VIN, ENL, and AGND pins.
13