LTC3836 LINER [Linear Technology], LTC3836 Datasheet - Page 18

• Manufacturer Part Number: LTC3836
• Description: Dual 2-Phase, No RSENSETM Low VIN Synchronous Controller
• Manufacturer: LINER [Linear Technology]

LTC3836
APPLICATIONS INFORMATION
During soft-start, the start-up of V
slowly ramping the positive reference to the error amplifi er
from 0V to 0.6V, allowing V
to its fi nal value. The default internal soft-start time is 1ms.
This can be increased by placing a capacitor between the
RUN/SS pin and SGND. In this case, the soft-start time
will be approximately:
Tracking
The start-up of V
TRACK/SS2 pin. Normally this pin is used to allow the start-
up of V
in Figures 7a and 7b. When the voltage on the TRACK/SS2
pin is less than the internal 0.6V reference, the LTC3836
18
t
SS1
OUT2
= C
SS
to track that of V
•
0.65μA
600mV
OUT2
is controlled by the voltage on the
(7b) Coincident Tracking
OUT1
OUT1
Figures 7b and 7c. Two Different Modes of Output Voltage Tracking
to rise smoothly from 0V
TIME
as shown qualitatively
OUT1
is controlled by
R
R
Figure 7a. Using the TRACK/SS Pin
TRACKB
TRACKA
V
V
OUT1
OUT2
V
OUT1
R1B
R1A
V
TRACK/SS2
FB1
LTC3836
regulates the V
instead of 0.6V. The start-up of V
track that of V
divider (Figure 7c):
For coincident tracking (V
The ramp time for V
value is:
R2A = R
R2B = R
t
V
V
V
SS2
OUT2
FB2
OUT1
3836 F07a
= t
V
OUT2
=
SS1
TRACKA
TRACKB
(7c) Ratiometric Tracking
R2B
R2A
R
TRACKA
OUT1
R2A
•
FB2
V
OUT1F
0.6
voltage to the TRACK/SS2 pin voltage
, according to a ratio set by a resistor
TIME
•
OUT2
R
•
TRACKA
R
OUT1
TRACKA
R2B + R2A
to rise from 0V to its fi nal
= V
R
OUT2
+ R
TRACKA
3836 F07b_c
OUT2
+ R
TRACKB
V
V
may ratiometrically
OUT1
OUT2
TRACKB
during start-up),
3836fa