ir3841 International Rectifier Corp., ir3841 Datasheet - Page 14

• Manufacturer Part Number: ir3841
• Description: Integrated 8a Synchronous Buck Regulator
• Manufacturer: International Rectifier Corp.

Thermal Shutdown
Temperature sensing is provided inside IR3841.
The trip threshold is typically set to 140
trip threshold is exceeded, thermal shutdown
turns off both MOSFETs and discharges the soft
start capacitor.
Automatic restart is initiated when the sensed
temperature drops within the operating range.
There is a 20
shutdown threshold.
Output Voltage Sequencing
The
programmable sequencing options using Seq,
Enable and Power Good pins.
Fig. 8a. Simultaneous Power-up of the slave
02/09/09
Through these pins, voltage sequencing such as
simultaneous
implemented. Figure 8. shows simultaneous
sequencing
power-up, the voltage at the Seq pin of the slave
reaches 0.7V before the Fb pin of the master. For
R
the slave follows that of the master until the
voltage at the Seq pin of the slave reaches 0.7 V.
After the voltage at the Seq pin of the slave
exceeds 0.85V, the internal 0.7V reference of
the slave dictates its output voltage.
E
/R
F
IR3841
with respect to the master.
=R
C
/R
Simultaneous Powerup
D
configurations.
o
, therefore, the output voltage of
C hysteresis in the thermal
can
and
accommodate
sequential
Vo1
Vo2
In
simultaneous
o
C. When
can
user
be
RE
RF
Vo(master)
1.5V <Vin<16V
4.5V <Vcc<5.5V
PGood
1.5V <Vin<16V
4.5V <Vcc<5.5V
PGood
Power Good Output
The IC continually monitors the output voltage via
Feedback (Fb pin). The feedback voltage is
compared to a fixed voltage. As soon as the Fb
voltage reaches 0.88*V
flags. This pin is open drain and it needs to be
externally pulled high. High state indicates that
output is in regulation. Fig 9. shows the timing
diagram for the PGood function.
Fig. 8b. Application Circuit for Simultaneous
Seq
Vcc
Rt
SS/ SD
PGood
Seq
Vcc
Rt
SS/ SD
PGood
Sequencing
Enable
Enable
Gnd
Gnd
Vin
PGnd
Vin
IR3841MPbF
PGnd
OCSet
Comp
Boot
OCSet
ref
Comp
SW
Fb
Boot
SW
Fb
, the Power Good signal
RA
RC
RB
RD
14
Vo(master)
Vo(slave)