ncp3121 ON Semiconductor, ncp3121 Datasheet - Page 3

• Manufacturer Part Number: ncp3121
• Description: Dual 3.0 A, Step-down Dc/dc Switching Regulator
• Manufacturer: ON Semiconductor

PIN DESCRIPTION
1, 31, 32
8 – 10
2 - 7
Pin
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Exposed Pad (GND)
TRACK 2
TRACK 1
Symbol
COMP2
COMP1
AGND
AGND
GND2
GND1
SEQ2
SEQ1
SW1
SW2
EN2
EN1
PG2
PG1
AV
SS2
FB2
FB1
SS1
V
RT
IN
IN
Switch node of Channel 1. Connect an inductor between SW1 and the regulator output.
Input power supply voltage pins. These pins should be connected together to the input signal sup‐
ply voltage pin.
Switch node of Channel 2. Connect an inductor between SW2 and the regulator output.
Power ground for Channel 2
Soft-start control input for Channel 2. An internal current source charges an external capacitor
connected to this pin to set the soft-start time.
Compensation pin of Channel 2. This is the output of the error amplifier and inverting input of the
PWM comparator.
Analog ground; connect to GND1 and GND2.
Feedback Pin. Used to set the output voltage of Channel 2 with a resistive divider from the output.
Resistor select for the oscillator frequency. Connect a resistor from the RT pin to AGND to set the
frequency of the master oscillator.
Tracking input for Channel 2. This pin allows the user to control the rise time of the second output.
This pin must be tied high in the normal operation (except in the tracking mode).
Tracking input for Channel 1. This pin allows the user to control the rise time of the first output. This
pin must be tied high in the normal operation (except in the tracking mode).
Sequence pin for Channel 2. I/O used in power sequencing. Connect SEQ to EN for normal opera‐
tion of a standalone device.
Enable input for Channel 2.
Sequence pin for Channel 1. I/O used in power sequencing. Connect SEQ to EN for normal opera‐
tion of a standalone device.
Enable input for Channel 1.
Power good, open-drain output of Channel 2. Output logic is pulled to ground when the output is
less than 90% of the desired output voltage. Tied to an external pull-up resistor.
Power good, open-drain output of Channel 1. Output logic is pulled to ground when the output is
less than 90% of the desired output voltage. Tied to an external pull-up resistor.
Input signal supply voltage pin.
Feedback Pin. Used to set the output voltage of Channel 1 with a resistive divider from the output.
Analog ground. Connect to GND1 and GND2.
Compensation pin of Channel 1. This is the output of the error amplifier and inverting input of the
PWM comparator.
Soft-start/stop control input for Channel 1. An internal current source charges an external capacitor
connected to this pin to set the soft-start time.
Power ground for Channel 1.
The exposed pad at the bottom of the package is the electrical ground connection of the NCP3121.
This node must be tied to ground.
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NCP3121
3
Description