IR3513Z International Rectifier Corp., IR3513Z Datasheet - Page 29

• Manufacturer Part Number: IR3513Z
• Description: Xphase3tm Pol Control Ic
• Manufacturer: International Rectifier Corp.

Bootstrap Capacitor C
Depending on the duty cycle and gate drive current of the phase IC, a capacitor in the range of 0.1uF to 1uF 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.
Over-voltage Resistors R
The over-voltage resistors are used to set the voltage at the OVSNS pin. If the voltage of the OVSNS pin exceeds
VREF by 85mV then the over-voltage protection will be activated and the error amplifier voltage will be pulled down
turning the converter off. The over-voltage fault is latched, which means that the power to the converter has to be
recycled for the fault to clear. Choose VOVSNS a certain value ∆V below VREF. VREF is typically 0.8 V. The over-
voltage threshold will then be ∆V+85mV. Select R
VREF Slew Rate Programming Capacitor C
The slew rate of MARGIN down-slope can be programmed by the external capacitor C
I
resistor R
Type III Compensation
Choose the crossover frequency fc between 1/10 and 1/5 of the switching frequency per phase, the desired phase
margin θc and Rfb1 (see Figure 17). Determine the component values based on the equations below. wc is 2*π*fc
(the crossover angular frequency), Le is the equivalent inductance of the converter, C is the output capacitance, Rst is
the total equivalent resistance in series with the inductor, Rc is the output capacitance ESR and R is the load
resistance.
SINK
is the sink current of the VREF pin. The slew rate of MARGIN up-slope is the same as that of down-slope. The
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VREF
is used to compensate the VREF circuit and can be calculated as shown in (18).
Ccp
Rcp
Ccp
Cfb
BST
1
C
R
R
=
=
=
VREF
=
OV
VREF
OV1
Ccp
wz
K
wp
2
=
⋅
2
and R
=
=
1
1
2
Rfb
⋅
1
⋅
V
VOVSNS
1
0
wz
⋅
SR
Rfb
OUT
5 .
Rcp
1
I
1
MARGIN
SINK
OV2
+
1
−
3
VOVSNS
2 .
C
VREF
∗
*
=
10
R
VREF
132
OV
SR
2
−
15
1
OV1.
MARGIN
*
and Resistor R
10
R
−
6
OV2
is calculated based on (16).
VREF
VREF
(16)
(17)
(18)
May 11, 2009
as defined in (17), where
(19)
(21)
(20)
(22)
IR3513Z