ncp3121 ON Semiconductor, ncp3121 Datasheet - Page 24

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

Tracking
the TRACK pin. When the voltage on the TRACK pin is
below 0.8 V, the feedback voltage will regulate to this
tracking voltage. When the tracking voltage exceeds 0.8 V,
tracking is disabled and the feedback voltage will regulate
to the internal reference voltage.
the output voltage ramps exactly. Higher output voltage will
continue to rise past the lower regulated point. This is
Disable
Voltage tracking is enabled by applying a ramp voltage to
In this start-up sequence, the tracking pin is used to match
C
master
Enable
VOUT1
VOUT2
R10
R9
PG1
PG2
EN1
SEQ1
EN2
SEQ2
TRACK1
TRACK2
AVIN
C
GND
master
C13
Figure 45. Tracking Configuration
NCP3121
C3
R8
R7
C4
GND
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Cmaster
NCP3121
GND
24
achieved by dividing the higher output voltage by the same
ratio as the lower voltage feedback components and
connecting the divided voltage into the TRACK pin of the
lower voltage. Track pins must be tied high in the normal
operation (except in the tracking mode).
the following equation:
V
SW1
SW2
The output voltage during tracking can be calculated with
VIN
VIN
VIN
VIN
VIN
VIN
OUT
R11
+ V
GND
TRACK
C9
GND
D1
D2
GND
1 ) R5
GND
GND
C10
L2
L1
R6
VIN
R1
R2
R3
R4
GND
GND
GND
C7
V
TRACK
C8
GND
R5
R6
GND
OUT1
OUT2
t 0.8 V