LTC3736EGN-2#PBF Linear Technology, LTC3736EGN-2#PBF Datasheet - Page 18

• Manufacturer Part Number: LTC3736EGN-2#PBF
• Description: IC CTRLR SW SYNC DUAL 2PH 24SSOP
• Manufacturer: Linear Technology
• Series: PolyPhase®r
• Type: Step-Down (Buck)r

Specifications of LTC3736EGN-2#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.6 ~ 9.8 V
• Current - Output: 1A
• Frequency - Switching: 550kHz ~ 750kHz
• Voltage - Input: 2.75 ~ 9.8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIONS INFORMATION
LTC3736-2
Run/Soft-Start Function
The RUN/SS pin is a dual purpose pin that provides the
optional external soft-start function and a means to shut
down the LTC3736-2.
Pulling the RUN/SS pin below 0.65V puts the LTC3736-2
into a low quiescent current shutdown mode (I
RUN/SS has been pulled all the way to ground, there will
be a delay before the LTC3736-2 comes out of shutdown
and is given by:
This pin can be driven directly from logic as shown in
Figure 6. Diode D1 in Figure 6 reduces the start delay
but allows C
function. This diode (and capacitor) can be deleted if the
external soft-start is not needed.
During soft-start, the start-up of V
slowly ramping the positive reference to the error ampli-
fi er from 0V to 0.6V, allowing V
0V to its fi nal value. The default internal soft-start time
is 1ms.
18
t
DELAY
3.3V OR 5V
=
SS
0 65
.
Figure 6. RUN/SS Pin Interfacing
Figure 5. Setting Output Voltage
1/2 LTC3736-2
to ramp up slowly providing the soft-start
V
D1
•
0 7
RUN/SS
V
C
.
V
FB
DD
SS
μ
≤ V
A
C
37362 F06
SS
IN
=
V
OUT1
0 93
OUT
.
R
R
37362 F05
B
A
s F C
to rise smoothly from
OUT1
RUN/SS
/
μ
C
(INTERNAL SOFT-START)
FF
•
is controlled by
SS
Q
= 9μA). If
RUN/SS
C
SS
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 pin. Normally this pin is used to allow the start-up
of V
Figures 7a and 7b. When the voltage on the TRACK pin
is less than the internal 0.6V reference, the LTC3736-2
regulates the V
stead of 0.6V. The start-up of V
track that of V
divider (Figure 7c):
For coincident tracking (V
The ramp time for V
is:
R2A = R
R2B = R
t
t
V
V
SS
SS
OUT2
OUT
OUT
1
2
=
=
2
1
to track that of V
C
=
t
TRACKA
TRACKB
SS
SS
R
R
TRACKB
TRACKA
R
1
OUT1
TRACKA
•
R A
Figure 7a. Using the TRACK Pin
•
FB2
600
R
0 7
2
OUT2
.
TRACKA
, according to a ratio set by a resistor
R A
voltage to the TRACK pin voltage in-
V
mV
μ
OUT2
1
OUT1
A
is controlled by the voltage on the
•
R1B
R1A
R
to rise from 0V to its fi nal value
TRACKA
OUT1
•
OUT1
V
TRACK
R
LTC3736-2
FB1
R B R A
TRACKA
2
= V
as shown qualitatively in
OUT2
V
R A R B
+
+
FB2
OUT2
1
R
37362 F07a
2
TRACKB
may ratiometrically
+
+
V
OUT2
R
during start-up),
R2B
R2A
1
TRACKB
37362fb