DC823B-B Linear Technology, DC823B-B Datasheet - Page 8

• Manufacturer Part Number: DC823B-B
• Description: BOARD EVAL LTM4600HV
• Manufacturer: Linear Technology
• Series: µModuler

Specifications of DC823B-B

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.2V, 1.5V, 1.8V, 2.5V, 3.3V, 5V
• Current - Output: 10A (Max)
• Voltage - Input: 4.5 V ~ 28 V
• Regulator Topology: Buck
• Frequency - Switching: 1.35MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LTM4600HV
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

OPERATIO
LTM4600HV
μModule Description
The LTM4600HV is a standalone non-isolated synchronous
switching DC/DC power supply. It can deliver up to 10A of
DC output current with only bulk external input and output
capacitors. This module provides a precisely regulated
output voltage programmable via one external resistor from
0.6V
A simplifi ed block diagram is shown in Figure 1 and the
typical application schematic is shown in Figure 21.
The LTM4600HV contains an integrated LTC constant
on-time current-mode regulator, ultra-low R
with fast switching speed and integrated Schottky diode.
The typical switching frequency is 850kHz at full load.
With current mode control and internal feedback loop
compensation, the LTM4600HV module has suffi cient
stability margins and good transient performance under a
wide range of operating conditions and with a wide range
of output capacitors, even all ceramic output capacitors
(X5R or X7R for extended temperature range).
Current mode control provides cycle-by-cycle fast current
limit. In addition, foldback current limiting is provided
in an over-current condition while V
the LTM4600HV has defeatable short circuit latch off.
Internal overvoltage and undervoltage comparators pull
the open-drain PGOOD output low if the output feedback
voltage exits a ±10% window around the regulation point.
Furthermore, in an overvoltage condition, internal top FET
8
DC
to 5.0V
DC
. The input voltage range is 4.5V to 28V.
U
OSET
drops. Also,
DS(ON)
FETs
Q1 is turned off and bottom FET Q2 is turned on and held
on until the overvoltage condition clears.
Pulling the RUN/SS pin low forces the controller into its
shutdown state, turning off both Q1 and Q2. Releasing the
pin allows an internal 1.2μA current source to charge up
the softstart capacitor. When this voltage reaches 1.5V,
the controller turns on and begins switching.
At low load current the module works in continuous cur-
rent mode by default to achieve minimum output voltage
ripple. It can be programmed to operate in discontinuous
current mode for improved light load effi ciency when the
FCB pin is pulled up above 0.8V and no higher than 6V.
The FCB pin has a 4.75k resistor to ground, so a resistor
to V
When EXTV
linear regulator powers the controller and MOSFET gate
drivers. If a minimum 4.7V external bias supply is ap-
plied on the EXTV
off, and an internal switch connects EXTV
driver voltage. This eliminates the linear regulator power
loss with high input voltage, reducing the thermal stress
on the controller. The maximum voltage on EXTV
6V. The EXTV
V
Recommended for 24V operation to lower temperature
in the μModule.
IN
IN
voltage. Also EXTV
can set the voltage on the FCB pin.
CC
CC
pin is grounded or open, an integrated 5V
voltage should never be higher than the
CC
pin, the internal regulator is turned
CC
must be sequenced after V
CC
to the gate
CC
4600hvfc
pin is
IN
.