DC1084A-A Linear Technology, DC1084A-A Datasheet - Page 13

• Manufacturer Part Number: DC1084A-A
• Description: LTM4602EV1 UMODULE DEMO BOARD
• Manufacturer: Linear Technology
• Series: µModuler

Specifications of DC1084A-A

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Power - Output: -
• Voltage - Output: 1.2V, 1.5V, 1.8V, 2.5V, 3.3V, 5V
• Current - Output: 6A
• Voltage - Input: 4.5 ~ 20 V
• Regulator Topology: Buck
• Frequency - Switching: 800kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LTM4602
• Lead Free Status / Rohs Status: Not applicable / Not applicable

APPLICATIONS INFORMATION
Enable
The RUN/SS pin can be driven from logic as shown in
Figure 5. This function allows the LTM4602 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 LTM4602 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
Figure 6. Output Voltage Tracking with the LTC2923 Controller
IN
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
GATE
2N7002
LTC2923
Q1
GND
STATUS
RAMP
SDO
FB1
FB2
RUN/SS
PGND
LTM4602
3.3V
SGND
R
66.5k
R
49.9k
4602 F06
SET
SET
4602 F05
V
V
OSET
OSET
LTM4602
LTM4602
OUT
V
V
V
V
IN
IN
IN
IN
rising and
V
V
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 LTM4602 can be directly powered by V
driver current through LDO is about 18mA. The internal
LDO power dissipation can be calculated as:
The LTM4602 also provides an external gate driver volt-
age pin EXTV
recommended to connect EXTV
rail. Whenever the EXTV
nal 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 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-
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
CC
= 18mA • (V
. If there is a 5V rail in the system, it is
CC
CC
until this pin drops below 4.5V. Do
CC
:
CC
voltage can not be higher than
CC
IN
pin is above 4.7V, the inter-
– 5V)
to internal 5V. Internal 5V is
CC
pin to the external 5V
CC
pin and ensure that
LTM4602
IN
. The gate
13
4602fa