IR3623MPBF_1 IRF [International Rectifier], IR3623MPBF_1 Datasheet - Page 9

• Manufacturer Part Number: IR3623MPBF_1
• Description: HIGH FREQUENCY 2-PHASE, SINGLE OR DUAL OUTPUT SYNCHRONOUS STEP DOWN CONTROLLER WITH OUTPUT TRACKING AND SEQUENCING
• Manufacturer: IRF [International Rectifier]

Circuit Description
THEORY OF OPEARTION
Introduction
The IR3623 is a versatile device for high
performance buck converters. It consists of two
synchronous buck controllers which can be
operated either in two independent outputs mode
or in current share single output mode for high
current applications.
The timing of the IC is provided by an internal
oscillator circuit which generates two-180
phase clock that can be externally programmed
up to 1200kHz per phase.
The IR3623 when combined with IR’s iPOWIR
power stage modules offers a compact and
efficient solution where integration and power
density are desired.
Under-Voltage Lockout
The under-voltage lockout circuit monitors three
signals (Vcc, Enable and 5V_sns). This ensures
the correct operation of the converter during
power up and power down sequence. The PWM
outputs remain in the off state whenever one of
these signals drop below set thresholds. Normal
operation resumes once these signals rise above
the set values. Figure 3 shows a typical start up
sequence.
www.irf.com
5V_sns
Enable
Vout3
Vbus
SS
Seq
Vcc
11V
8.0V
4.7V
Fig. 3: Normal Start up, Enable threshold is externally set to 11V
o
-out-of-
5V_sns
IR3623 integrates an internal LDO for powering
the external module without need for an external
supply. For a correct start up sequence the
external module needs to be biased first prior to
the controller IC. The V
Vcc is applied but the POR (Power On Ready) is
not enabled until the V
threshold set by 5V_sns pin.
Enable
The enable features another level of flexibility for
start up. The Enable has precise threshold which
is internally monitored by under-voltage lockout
circuit.
It’s threshold can be externally programmed to
desired level by using two external resistors, so
the converter doesn’t start up until the input
voltage is sufficiently high.
5.2V
3V
12V
12V
out3
V
V
Enable OK (IC's POR)
IR3623MPbF
out3
cc
out3
OK
OK
ramps up as soon as
reached the 5V
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