4
dc1185b-a/-bf
DEMO MANUAL
DC1185B-A/-B
RAIL TRACKING
Demonstration circuit 1185 is set up for independent
turn-on of VOUT1 and VOUT2. The ramp-rate for VOUT1 is
determined by the TRK/SS1 capacitor at C2 and the ramp-
rate for VOUT2 is determined by the TRK/SS2 capacitor
at C47. The turn-on of one rail will not affect the other for
the original demo board.
This board can be modified on the bench to allow VOUT1
to track an external signal. It can also be modified to
allow VOUT2 to track VOUT1 or to allow VOUT2 to track
an external signal. Tables 2 and 3 cover the rail tracking
options for each rail, with the DC3850B-B version used
as an example.
Table 1. VOUT1 Tracking Options for a 1.5V Output
TRACK 1 DIVIDER
TRK/SS1 CAPACITOR
CONFIGURATION
R3
R2
C2
Soft-Start without Tracking (Original Board)
0Ω
Not Stuffed
0.1µF
External Coincident Tracking
17.8kΩ
20.0kΩ
Not Stuffed
Table 2. VOUT2 Tracking Options for a 1.2V Output
TRACK 2 DIVIDER
TRK/SS2 CAPACITOR
CONFIGURATION
R36
R34
R37
C47
Soft-Start without Tracking (Original Board)
0Ω
Not Stuffed
Not Stuffed
0.1µF
Coincident Tracking to VOUT1 (1.5V)
0Ω
10.0kΩ
20.0kΩ
Not Stuffed
External Coincident Tracking
10.0kΩ
Not Stuffed
20.0kΩ
Not Stuffed
