IR3081 International Rectifier Corp., IR3081 Datasheet - Page 29

• Manufacturer Part Number: IR3081
• Description: Xphasetm Vr 10 Control Ic
• Manufacturer: International Rectifier Corp.

DESIGN EXAMPLE 2 - EVRD 10 HIGH FREQUENCY ALL-CERAMIC CONVERTER
SPECIFICATIONS
Input Voltage: V
DAC Voltage: V
No Load Output Voltage Offset: V
Output Current: I
Maximum Output Current: I
Output Impedance: R
VCC Ready to VCC Power Good Delay: t
Soft Start Time: t
Over Current Delay: t
Dynamic VID Down-Slope Slew Rate: SR
Over Temperature Threshold: T
POWER STAGE
Phase Number: n=6
Switching Frequency: f
Output Inductors: L=100 nH, R
Output Capacitors: Ceramic, C=22uF, R
IR3081 EXTERNAL COMPONENTS
Oscillator Resistor Rosc
Once the switching frequency is chosen, R
switching frequency of 800kHz per phase, choose R
Soft Start Capacitor C
Because faster over-current protection is required, the soft start capacitor C
R
Calculate the soft start resistor from the required over current delay time t
The soft start delay time is
The power good delay time is
C
t
t
R
VccPG
SSDEL
SS/DEL
SS
SS
/
/
Page 29 of 39
DEL
DEL
=
=
=
=
C
C
is used. Calculate the soft start capacitor from the required soft start time.
SS
SS
. 0
I
CHG
09
/
/
DEL
DEL
V
O
−
∗
DAC
I
t
∗
=12 V
t
∗
O
SS
OCDEL
SS
I
(
1 (
I
=105 ADC
DISCHG
. 3
CHG
=2.9mS
=1.3 V
3 .
=
C
91
I
OCDEL
O
SS
−
70
CHG
∗
−
=0.91 mΩ
SW
SS/DEL
/
R
I
V
DEL
*
1
SS
DISCHG
10
3 .
O
=800 kHz
/
OMAX
=2.1mS
−
−
DEL
−
6
1
20
∗
) 3 .
and Resistor R
L
∗
2
*
PCB
=0.5 mΩ
=
=120 ADC
9 .
10
I
=
O_NLOFST
CHG
. 0
*
−
. 0
=115 ºC
10
09
3
15
)
−
−
3
=
*
C
. 2
=
10
. 0
VccPG
DOWN
= 2mΩ, Number Cn=62
* 1
6
. 0
15
=20 mV
−
*
. 0
16
6
10
10
70
OSC
*
15
( *
uF
SS/DEL
−
10
=0-10mS
−
=2.5mV/uS
*
3
. 3
*
6
10
∗
10
−
, choose C
91
can be determined from the curve in Figure 13 data sheet. For
6
6
−
∗
*
−
−
6
OSC
6
10
1 (
. 1
70
3 .
−
28
6
=13.3kΩ
*
−
10
−
=
1
. 1
*
1
−
SS/DEL
k
10
6
) 3
Ω
3
=
*
. 2
70
=0.15uF
85
*
ms
10
−
6
OCDEL
)
=
2
6 .
,
mS
SS/DEL
in series with the resistor
10/01
IR3081
/04