LTM4600IV#PBF Linear Technology, LTM4600IV#PBF Datasheet - Page 13

• Manufacturer Part Number: LTM4600IV#PBF
• Description: IC DC/DC UMODULE 10A 104-LGA
• Manufacturer: Linear Technology
• Series: µModuler
• Type: Point of Load (POL) Non-Isolatedr

Specifications of LTM4600IV#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
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 LTM4600 can be directly powered by V
driver current through LDO is about 18mA. The internal
LDO power dissipation can be calculated as:
P
The LTM4600 also provides an external gate driver volt-
age pin EXTV
recommended to connect EXTV
rail. Whenever the EXTV
5V LDO is shut off and an internal 50mA P-channel switch
connects the EXTV
from EXTV
more than 6V to the EXTV
< V
tions for EXTV
Output Voltage Tracking
For the applications that require output voltage tracking,
several LTM4600 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.
LDO_LOSS
Figure 6. Output Voltage Tracking with the LTC2923 Controller
IN
V
5V
IN
. The following list summaries the possible connec-
CC
R
R
TB1
TA1
Connection
DC/DC
CC
= 18mA • (V
R
R
R
R
ONB
ONA
TB2
TA2
until this pin drops below 4.5V. Do not apply
CC
CC
. If there is a 5V rail in the system, it is
:
CC
ON
RAMPBUF
TRACK1
TRACK2
V
CC
to internal 5V. Internal 5V is supplied
GATE
IN
LTC2923
Q1
CC
GND
– 5V)
CC
pin is above 4.7V, the internal
STATUS
pin and ensure that EXTV
RAMP
SDO
FB1
FB2
CC
3.3V
pin to the external 5V
49.9k
66.5k
4600 F06
V
V
OSET
OSET
LTM4600
LTM4600
V
V
V
V
IN
IN
IN
IN
O
IN
V
V
OUT
OUT
. The gate
rising and
1.8V
1.5V
CC
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 4.75k pull-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 the application where the light load effi ciency is im-
portant, tying the FCB pin above 0.6V threshold enables
discontinuous operation where the bottom MOSFET turns
off when inductor current reverses. Therefore, the conduc-
tion loss is minimized and light load effi ciency is improved.
The penalty is that the controller may skip cycle and the
output voltage ripple increases at light load.
Paralleling Operation with Load Sharing
Two or more LTM4600 modules can be paralleled to provide
higher than 10A output current. Figure 7 shows the neces-
sary interconnection between two paralleled modules. The
OPTI-LOOP
sharing among modules to balance the thermal stress.
The new feedback equation for two or more LTM4600s
in parallel is:
where N is the number of LTM4600s in parallel.
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
IN
V
pin voltage.
OUT
CC
CC
= 0.6V •
grounded. Internal 5V LDO is always powered
connected to an external supply. Internal LDO
®
current mode control ensures good current
100k
N
R
CC
SET
+ R
voltage can not be higher than
SET
LTM4600
13
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