LTC3716EG Linear Technology, LTC3716EG Datasheet - Page 18

• Manufacturer Part Number: LTC3716EG
• Description: IC SW REG STP-DN 5BIT SYNC36SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3716EG

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 1.75 V
• Current - Output: 35mA
• Frequency - Switching: 120kHz ~ 310kHz
• Voltage - Input: 4 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
LTC3716
Table 1. VID Output Voltage Programming
18
Soft-Start/Run Function
The RUN/SS pin provides three functions: 1) Run/Shut-
down, 2) soft-start and 3) a defeatable short-circuit latchoff
timer. Soft-start reduces the input power sources’ surge
currents by gradually increasing the controller’s current
limit I
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
TH(MAX)
VID3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
. The latchoff timer prevents very short,
U
VID2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
U
VID1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
W
VID0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
LTC3716
U
1.750V
1.700V
1.650V
1.600V
1.550V
1.500V
1.450V
1.400V
1.350V
1.300V
1.250V
1.200V
1.150V
1.100V
1.050V
1.000V
0.975V
0.950V
0.925V
0.900V
0.875V
0.850V
0.825V
0.800V
0.775V
0.750V
0.725V
0.700V
0.675V
0.650V
0.625V
0.600V
extreme load transients from tripping the overcurrent
latch. A small pull-up current (>5 A) supplied to the RUN/
SS pin will prevent the overcurrent latch from operating.
The following explanation describes how the functions
operate.
An internal 1.2 A current source charges up the soft-start
capacitor, C
the controller is permitted to start operating. As the voltage
on RUN/SS increases from 1.5V to 3.0V, the internal
current limit is increased from 25mV/R
R
an additional 1.4s/ F to reach full current. The output
current thus ramps up slowly, reducing the starting surge
current required from the input power supply. If RUN/SS
has been pulled all the way to ground there is a delay before
starting of approximately:
The time for the output current to ramp up is then:
By pulling the RUN/SS pin below 0.8V the LTC3716 is put
into low current shutdown (I
can be driven directly from logic as shown in Figure 6.
Diode D1 in Figure 6 reduces the start delay but allows
C
The RUN/SS pin has an internal 6V zener clamp (see
Functional Diagram).
SS
SENSE
3.3V OR 5V
*OPTIONAL TO DEFEAT OVERCURRENT LATCHOFF
t
t
DELAY
IRAMP
to ramp up slowly providing the soft-start function.
. The output current limit ramps up slowly, taking
D1
SS
1 2
3
1 5
. When the voltage on RUN/SS reaches 1.5V,
.
V
Figure 6. RUN/SS Pin Interfacing
.
1 2
V
IN
.
V
R
A
1 5
SS
.
C
A
*
RUN/SS
SS
V
C
C
SS
SS
1 25
.
Q
< 40 A). The RUN/SS pins
1 25
s F C
.
/
D1*
s F C
INTV
/
SS
CC
R
SENSE
SS
*
SS
RUN/SS
to 75mV/
3716 F06
C
SS