IR3502MPBF International Rectifier, IR3502MPBF Datasheet - Page 26

• Manufacturer Part Number: IR3502MPBF
• Description: Complete VR11.0 or VR11.1 power solution.
• Manufacturer: International Rectifier

Specifications of IR3502MPBF

• Package: 32-Lead MLPQ
• Circuit: X-Phase Control IC
• Switch Freq (khz): 250kHz to 1.5MHz
• Pbf: PbF Option Available

DESIGN PROCEDURES - IR3502 AND IR3507 CHIPSET
IR3502 EXTERNAL COMPONENTS
Oscillator Resistor Rosc
The oscillator of IR502 generates square-wave pulses to synchronize the phase ICs. The switching frequency of
the each phase converter equals the PHSOUT frequency, which is set by the external resistor R
the curve in Figure 18. The CLKOUT frequency equals the switching frequency multiplied by the phase number.
The Rosc sets the reference current used for no load offset which is given by Figure 19 and equals:
Soft Start Capacitor C
The soft start capacitor C
start time, VID sample delay time, VR ready delay time and over-current fault latch delay time after VR ready.
For the converter using VID with boot voltage, the SS/DEL pin voltage controls the slew rate of the converter
output voltage, as shown in Figure 9. After the ENABLE pin voltage rises above 0.85V, there is a soft-start delay
time TD1
time TD2 represents the time during which converter voltage rises from zero to 1.1V
(TD3) is the time period when VID stays at boot voltage of 1.1V. VID rise or fall time (TD4) is the time when VID
changes from boot voltage to the final voltage. The VR ready delay time (TD5) is the time period from VR
reaching the final voltage to the VR ready signal being issued, which is determined by the delay comparator
threshold.
C
SS/DEL
= 0.1uF meets all the specifications of TD1 to TD5, which are determined by (2) to (6) respectively.
Page 26 of 39
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after which the error amplifier output is released to allow the soft start of output voltage. The soft start
SS/DEL
SS/DEL
TD
TD
TD
5
programs five different time parameters. They include soft start delay time, soft
4
3
=
=
=
C
C
TD
TD
C
SS
SS
SS
/
1
DEL
2
/
/
=
ISETPT
DEL
DEL
=
I
( *
CHG
C
C
I
*
. 3
SS
*
CHG
SS
I
3 (
92
CHG
V
/
I
I
/
DEL
CHG
DAC
−
DEL
CHG
−
=
1
) 3
4 .
. 0
Rosc
1 *
1 *
−
595
−
−
1
4 .
TD
1
1 .
1 .
) 1 .
=
=
4
=
C
=
=
C
52
C
52
SS
C
SS
C
SS
52
5 .
52
SS
/
5 .
SS
/
DEL
/
DEL
/
*
5 .
5 .
/
DEL
*
DEL
52
DEL
10
10
*
*
1 *
5 .
10
10
*
1 *
−
*
−
*
6
. 0
*
4 .
6
−
0
−
V
1 .
10
6
92
6
7 .
DAC
−
−
6
TD
.
−
The VID sample delay time
1
4
1 .
July 28, 2009
OSC
IR3502
according to
(1)
(2)
(3)
(4)
(5)
(6)