ltm4602hv Linear Technology Corporation, ltm4602hv Datasheet - Page 13

• Manufacturer Part Number: ltm4602hv
• Description: 6a, 28vin High Efficiency Dc/dc ?module
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Enable
The RUN/SS pin can be driven from logic as shown in
Figure 5. This function allows the LTM4602HV to be
turned on or off remotely. The ON signal can also control
the sequence of the output voltage.
Output Voltage Tracking
For the applications that require output voltage tracking,
several LTM4602HV modules can be programmed by the
power supply tracking controller such as the LTC2923.
Figure 6 shows a typical schematic with LTC2923. Coin-
cident, ratiometric and offset tracking for V
falling can be implemented with different sets of resistor
values. See the LTC2923 data sheet for more details.
V
5V
IN
Figure 6. Output Voltage Tracking with the LTC2923 Controller
R
R
TB1
TA1
DC/DC
R
R
R
R
Figure 5. Enable Circuit with External Logic
ONB
ONA
TB2
TA2
ON
ON
RAMPBUF
TRACK1
TRACK2
V
CC
U
GATE
2N7002
LTC2923
Q1
GND
U
STATUS
RAMP
SDO
FB2
FB1
RUN/SS
PGND
LTM4602HV
3.3V
4602HV
W
SGND
R
49.9k
R
66.5k
4602HV F06
F05
SET
SET
V
V
LTM4602HV
OSET
LTM4602HV
OSET
V
IN
V
V
V
O
IN
IN
IN
rising and
V
V
U
OUT
OUT
1.8V
1.5V
EXTV
An internal low dropout regulator produces an internal 5V
supply that powers the control circuitry and FET drivers.
Therefore, if the system does not have a 5V power rail,
the LTM4602HV can be directly powered by V
driver current through LDO is about 16mA. The internal
LDO power dissipation can be calculated as:
The LTM4602HV also provides an external gate driver
voltage pin EXTV
is recommended to connect EXTV
5V rail. Whenever the EXTV
ternal 5V LDO is shut off and an internal 50mA P-channel
switch connects the EXTV
supplied from EXTV
not apply more than 6V to the EXTV
EXTV
connections for EXTV
1. EXTV
from the internal 5V regulator.
2. EXTV
is shut off. A high effi ciency supply compatible with the
MOSFET gate drive requirements (typically 5V) can im-
prove overall effi ciency. With this connection, it is always
required that the EXTV
V
Discontinuous Operation and FCB Pin
The FCB pin determines whether the internal bottom
MOSFET remains on when the inductor current reverses.
There is an internal 10k pulling down resistor connecting
this pin to ground. The default light load operation mode
is forced continuous (PWM) current mode. This mode
provides minimum output voltage ripple.
IN
P
pin voltage.
LDO_LOSS
CC
CC
CC
CC
Connection
< V
grounded. Internal 5V LDO is always powered
connected to an external supply. Internal LDO
IN
. The following list summaries the possible
= 16mA • (V
CC
. If there is a 5V rail in the system, it
CC
CC
until this pin drops below 4.5V. Do
CC
:
voltage can not be higher than
CC
IN
CC
– 5V)
to internal 5V. Internal 5V is
pin is above 4.7V, the in-
LTM4602HV
CC
CC
pin and ensure that
pin to the external
IN
. The gate
13
4602hvf