LTM4600EV#PBF Linear Technology, LTM4600EV#PBF Datasheet - Page 12

• Manufacturer Part Number: LTM4600EV#PBF
• Description: IC DC/DC UMODULE 10A 104-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4600EV#PBF

• Design Resources: LTM4600 Spice Model
• Output: 0.6 ~ 5 V
• Number Of Outputs: 1
• Power (watts): 50W
• Mounting Type: Surface Mount
• Voltage - Input: 4.5 ~ 20V
• Package / Case: 104-LGA
• 1st Output: 0.6 ~ 5 VDC @ 10A
• Size / Dimension: 0.59" L x 0.59" W x 0.11" H (15mm x 15mm x 2.8mm)
• Power (watts) - Rated: 50W
• Operating Temperature: -40°C ~ 85°C
• Efficiency: 92%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• 3rd Output: -
• 2nd Output: -

APPLICATIONS INFORMATION
LTM4600
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 over-current protection timer requires the soft-start
timing capacitor C
that the output is in regulation by the time C
the 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
shortcircuit, over-current latchoff operation is NOT always
needed or desired, especially if the output has a large
amount of capacitance or the load draws huge currents
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 currents prevents the
discharge of C
start period. Using a resistor from RUN/SS pin to V
a simple solution to defeat latchoff. Any pull-up network
must be able to maintain RUN/SS above 4V maximum
latchoff threshold and overcome the 4μA maximum dis-
charge current. Figure 3 shows a conceptual drawing of
V
12
RUN
C
SS EXT
during startup and short circuit.
+ 1000pF > C
SS
during a fault and also shortens the soft-
SS
SS
be made large enough to guarantee
. If the fault condition persists until
OUT
• V
OUT
(10
–3
SS
SS
[F / V
is used as a
has reached
S
])
IN
is
Enable
The RUN/SS pin can be driven from logic as shown in
Figure 5. This function allows the LTM4600 to be turned
on or off remotely. The ON signal can also control the
sequence of the output voltage.
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
Figure 5. Enable Circuit with External Logic
3V
SOFT-START
CLAMPING
L
RELEASED
R
V
RUN/SS
ON
IN
4V
IN
RECOMMENDED VALUES FOR R
SHORT-CIRCUIT
LATCH ARMED
10.8V TO 13.8V
2N7002
4.5V TO 5.5V
16V TO 20V
V
RUN/SS
V
V
PGND SGND
IN
O
IN
V
RUN/SS
LTM4600
OVERLOAD
RUN/SS
HAPPENS
OUTPUT
PGND
4600 F04
R
LTM4600
RUN/SS
150k
330k
50k
SGND
4600 F05
RUN/SS
SHORT-CIRCUIT
75%V
LATCHOFF
O
3.5V
4600fc
4600 F03
t
t