IR3081AM IRF [International Rectifier], IR3081AM Datasheet - Page 22

• Manufacturer Part Number: IR3081AM
• Description: XPHASETM VR 10 CONTROL IC
• Manufacturer: IRF [International Rectifier]

Phase Delay Timing Resistors R
The phase delay of the interleaved multiphase converter is programmed by the resistor divider connected at
RMPIN+ or RMPIN- depending on which slope of the oscillator ramp is used for the phase delay programming of
phase IC, as shown in Figure 3.
If the upslope is used, RMPIN+ pin of the phase IC should be connected to RMPOUT pin of the control IC and
RMPIN- pin should be connected to the resistor divider. When RMPOUT voltage is above the trip voltage at
RMPIN- pin, the PWM latch is set. GATEL becomes low, and GATEH becomes high after the non-overlap time.
If down slope is used, RMPIN- pin of the phase IC should be connected to RMPOUT pin of the control IC and
RMPIN+ pin should be connected to the resistor divider. When RMPOUT voltage is below the trip voltage at
RMPIN- pin, the PWM latch is set. GATEL becomes low, and GATEH becomes high after the non-overlap time.
Use VBIAS voltage as the reference for the resistor divider since the oscillator ramp magnitude from control IC
tracks VBIAS voltage. Try to avoid both edges of the oscillator ramp for better noise immunity. Determine the ratio
of the programming resistors corresponding to the desired switching frequencies and phase numbers. If the resistor
R
Combined Over Temperature and Phase Delay Setting Resistors R
The over temperature setting resistor divider can be combined with the phase delay resistor divider to save one
resistor per phase.
Calculate the HOTSET threshold voltage V
Equation (18). If the over temperature setting voltage is lower than the phase delay setting voltage,
VBIAS*RA
between R
If the over temperature setting voltage is higher than the phase delay setting voltage, VBIAS*RA
HOTSET pin between R
respectively. Pre-select R
Bootstrap Capacitor C
Depending on the duty cycle and gate drive current of the phase IC, a 0.1uF to 1uF capacitor is needed for the
bootstrap circuit.
Decoupling Capacitors for Phase IC
0.1uF-1uF decoupling capacitors are required at VCC and VCCL pins of phase ICs.
PHASEx1
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is pre-selected, the resistor R
PHASEx
PHASEx2
, connect RMPIN+ or RMPIN- pin between R
and R
R
R
R
R
R
PHASEx
PHASEx
PHASEx
PHASEx
PHASEx
BST
PHASEx1
PHASEx3
PHASEx1
3
3
2
2
2
=
=
=
=
=
V
(
RA
RA
(
RA
V
V
BIAS
HOTSET
HOTSET
PHASEx
. Pre-select R
and R
PHASEx
,
1
PHASEx
PHASE1
V
−
*
BIAS
1 (
RA
V
−
∗
∗
PHASEx2
BIAS
−
PHASEx2
∗
PHASEx
∗
V
RA
−
R
V
RA
R
V
BIAS
PHASEx
V
and R
BIAS
PHASEx
PHASEx
BIAS
HOTSET
∗
PHASEx
1 (
*
HOTSET
−
−
PHASEx1
−
R
1
V
and connect RMPIN+ or RMPIN- between R
1
V
PHASEx
is determined as:
RA
)
PHASE2
HOTSET
HOTSET
∗
PHASEx
V
BIAS
1
corresponding to the allowed maximum temperature from
,
* )
)
)
∗
R
R
PHASEx
PHASEx
1
PHASEx1
1
PHASE1,
and R
R
PHASEx2,
PHASE2
and R
and connect HOTSET pin
(20)
(21)
(22)
(23)
(24)
PHASEx2
PHASE3
IR3081A
1/31
PHASEx
and R
/05
, connect
PHASEx3