IR3086AM International Rectifier, IR3086AM Datasheet - Page 14

• Manufacturer Part Number: IR3086AM
• Description: XPHASE Phase IC with OVP with fault overtemp detect. The IR3086AM Phase IC combined with an IR XPhase TM Control IC provides a full featured and flexible way to implement power solutions for the latest high performance CPUs and ASICs.
• Manufacturer: International Rectifier

Specifications of IR3086AM

• Package: 20-Lead MLPQ
• Circuit: X-Phase Phase IC
• Iout (a): 2.5A Gate Driver
• Pbf: PbF Option Available

DESIGN PROCEDURES – IR3081A AND IR3086A CHIPSET
IR3081A EXTERNAL COMPONENTS
Oscillator Resistor Rosc
The oscillator of IR3081A generates a triangle waveform to synchronize the phase ICs, and the switching frequency
of the each phase converter equals the oscillator frequency, which is set by the external resistor R
the curve in Figure 13 of IR3081A Data Sheet.
Soft Start Capacitor C
Because the capacitor C
over-current latch delay time, and power good delay time, they should be considered together while choosing
C
The SS/DEL pin voltage controls the slew rate of the converter output voltage, as shown in Figure 10 of IR3081A.
After the ENABLE pin voltage rises above 0.6V, there is a soft-start delay time
output is released to allow the soft start. The soft start time
rises from zero to V
Once C
delay time
and (4) respectively.
VDAC Slew Rate Programming Capacitor C
The slew rate of VDAC down-slope SR
Equation (5), where I
resistor R
slope SR
current of VDAC pin as shown in Figure15 of IR3081A Data Sheet.
SS/DEL
SS/DEL
.
Page 14 of 33
UP
VDAC
t
VccPG
is proportional to that of VDAC down-slope and is given by Equation (7), where I
is chosen, the soft start delay time
is used to compensate VDAC circuit and is determined by Equation (6). The slew rate of VDAC up-
from output voltage (V
O.
C
t
t
t
C
R
SR
VccPG
SSDEL
OCDEL
VDAC
VDAC
t
SS
SINK
SS
UP
SS/DEL
/
DEL
SS/DEL
can be programmed by an external capacitor, which is determined by Equation (1).






is the sink current of VDAC pin as shown in Figure 15 of IR3081A Data Sheet. The
I
C
C
0
C

SR
C
SOURCE
SS
5 .
SS
VDAC
I
SS
I
SINK
I
DOWN
CHG
/

/
I
/
OCDISCHG
DEL
DEL
programs four different time parameters, i.e. soft start delay time, soft start time,
CHG
DEL
3
V
2 .
C
O
*
*
1 *
VDAC
*

t
3 (
SS
. 0
10
3 .
8 .
115
DOWN
I



2

O
CHG
15
) in regulation to Power Good are fixed and shown in Equations (2), (3)
70
C
. 0

SS
065
70
*
C
/
VDAC
10
DEL
*
can be programmed by the external capacitor C
SS
V

10
40

O
/
V
6
DEL
1 *

O
*
6
*
t
and Resistor R

10
SSDEL,
3 .
t
*
SS
. 1
. 0

) 3
6
115

the over-current fault latch delay time
C
t
SS
SS
/
DEL
represents the time during which converter voltage
( *
VDAC
70
. 3
*
735
10


6
V
O
t
SSDEL,

. 1
) 3
after which the error amplifier
(1)
(2)
(3)
(4)
(5)
(6)
(7)
IR3086A
SOURCE
VDAC
2/13/09
OSC
t
OCDEL
as defined in
is the source
according to
, and the