IR3897MTRPBF International Rectifier, IR3897MTRPBF Datasheet - Page 22

• Manufacturer Part Number: IR3897MTRPBF
• Description: 4A Highly Integrated Single-Input Voltage, Synchronous Buck Regulator in a PQFN package.
• Manufacturer: International Rectifier

Specifications of IR3897MTRPBF

• Part Status: Active and Preferred
• Package: PQFN / 4 x 5
• Circuit: Single Output
• Iout (a): 4
• Switch Freq (khz): 0 - 1500
• Input Range (v): 1.0 - 16
• Output Range (v): 0.5 - 12
• Pbf: PbF Option Available

amplifier switches to Vref and the output voltage is
regulated with Vref.The final Vp voltage after sequencing
startup should between 0.7V ~ 3.3V.
Tracking and sequencing operations can be implemented
to be simultaneous or ratiometric (refer to Fig. 13 and 14).
Figure 12 shows typical circuit configuration for sequencing
operation. With this power‐up configuration, the voltage
at the Vp pin of the slave reaches 0.5V before the Fb pin of
the master. If R
achieved. That is, the output voltage of the slave follows
that of the master until the voltage at the Vp pin of the
slave reaches 0.5 V. After the voltage at the Vp pin of the
slave exceeds 0.5V, the internal 0.5V reference of the
slave dictates its output voltage. In reality the regulation
gradually shifts from Vp to internal Vref. The circuit shown
in Fig. 12 can also be used for simultaneous or ratiometric
tracking operation if Vref of the slave is connected to GND.
Table 2 summarizes the required conditions to achieve
simultaneous/ratiometric tracking or sequencing
operations.
Figure 12: Application Circuit for Simultaneous
22
E
/R
and Ratiometric Sequencing
F
=R
FEBRUARY 02, 2012 |DATA SHEET | Rev 3.2
C
/R
D
, simultaneous startup is
Single‐Input Voltage, Synchronous Buck Regulator
- 22 -
4A Highly Integrated SupIRBuck
Figure 13: Typical waveforms for sequencing mode of operation:
T
T
ABLE
RACKING AND
Figure 14: Typical waveforms in tracking mode of operation:
Normal
(Non‐sequencing,
Non‐tracking)
Simultaneous
Sequencing
Ratiometric
Sequencing
Simultaneous
Tracking
Ratiometric
Tracking
2:
Operating
1.2V
1.2V
(a)
(b)
(a)
(b)
R
Mode
EQUIRED
Vref=0.5V
S
Vcc
Vcc
EQUENCING
(a) simultaneous, (b) ratiometric
(a) simultaneous, (b) ratiometric
C
ONDITIONS FOR
Soft Start (slave)
Soft Start (slave)
Vref=0V (slave)
Enable (slave)
Enable (slave)
(Floating)
(Slave)
(F
0.5V
0.5V
0.5V
Vref
Vo2 (slave)
0V
0V
Vo2 (slave)
IG
Vo2 (slave)
Vo2 (slave)
.
12)
TM
S
IMULTANEOUS
Ramp up
Ramp up
Ramp up
Ramp up
from 0V
from 0V
from 0V
from 0V
Floating
Vp
Vo1 (master)
Vo1 (master)
Vo1 (master)
Vo1 (master)
IR3897
/R
Condition
R
R
Required
R
R
A
A
=R
>R
PD‐97663
F
F
ATIOMETRIC
/R
/R
R
R
=R
>R
E
E
―
C
C
/R
/R
B
B
/R
/R
C
C
>R
>R
/R
/R
F
F
D
D
E
E
D
D
/
/