LTM4602IV#PBF Linear Technology, LTM4602IV#PBF Datasheet - Page 12

• Manufacturer Part Number: LTM4602IV#PBF
• Description: IC DC/DC UMODULE 6A 104-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4602IV#PBF

• Design Resources: LTM4602 Spice Model
• Output: 0.6 ~ 5 V
• Number Of Outputs: 1
• Power (watts): 30W
• Mounting Type: Surface Mount
• Voltage - Input: 4.5 ~ 20V
• Package / Case: 104-LGA
• 1st Output: 0.6 ~ 5 VDC @ 6A
• Size / Dimension: 0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
• Power (watts) - Rated: 30W
• Operating Temperature: -40°C ~ 85°C
• Efficiency: 92%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -

APPLICATIONS INFORMATION
LTM4602
After the controller has been started and given adequate
time to charge up the output capacitor, C
short-circuit timer. After the RUN/SS pin charges above 4V,
if the output voltage falls below 75% of its regulated value,
then a short-circuit fault is assumed. A 1.8μA current then
begins discharging C
the RUN/SS pin drops to 3.5V, then the controller turns
off both power MOSFETs, shutting down the converter
permanently. The RUN/SS pin must be actively pulled
down to ground in order to restart operation.
The overcurrent protection timer requires the soft-start
timing capacitor C
that the output regulation by the time C
4V threshold. In general, this will depend upon the size of
the output capacitance, output voltage and load current
characteristic. A minimum external soft-start capacitor
can be estimated from:
Generally 0.1μF is more than suffi cient.
Since the load current is already limited by the current mode
control and current foldback circuitry during a short circuit,
overcurrent latchoff operation is NOT always needed or
desired, especially if the output has large capacitance or
the load draws high current during start up. The latchoff
feature can be overridden by a pull-up current greater than
5μA but less than 80μA to the RUN/SS pin. The additional
current prevents the discharge of C
also shortens the soft-start period. Using a resistor from
RUN/SS pin to V
pull-up network must be able to maintain RUN/SS above
12
C
SS_EXT
+ 1000pF > C
IN
is a simple solution to defeat latchoff. Any
SS
SS
be made large enough to guarantee
. If the fault condition persists until
OUT
• V
OUT
SS
(10
SS
during a fault and
–3
has reached the
SS
[F / V
is used as a
S
])
4V maximum latchoff threshold and overcome the 4μA
maximum discharge current. Figure 3 shows a conceptual
drawing of V
1.5V
SWITCHING
STARTS
Figure 3. RUN/SS Pin Voltage During Startup and
Short-Circuit Protection
Figure 4. Defeat Short-Circuit Latchoff with a Pull-Up
Resistor to V
OF I
3V
SOFT-START
CLAMPING
L
RELEASED
RUN
4V
IN
during start-up and short circuit.
RECOMMENDED VALUES FOR R
R
SHORT-CIRCUIT
LATCH ARMED
V
RUN/SS
IN
V
10.8V TO 13.8V
4.5V TO 5.5V
OUT
16V TO 20V
V
RUN/SS
V
IN
OVERLOAD
V
RUN/SS
HAPPENS
OUTPUT
PGND SGND
IN
LTM4602
R
RUN/SS
150k
330k
50k
RUN/SS
SHORT-CIRCUIT
4602 F04
75%V
LATCHOFF
O
3.5V
4602fa
4602 F03
t
t