isl6260c Intersil Corporation, isl6260c Datasheet - Page 27

• Manufacturer Part Number: isl6260c
• Description: Multiphase Pwm Regulator For Imvp-6 Mobile Cpus
• Manufacturer: Intersil Corporation

Fault Protection - Overcurrent Fault Setting
As previously described, the overcurrent protection of the
ISL6260C is related to the Droop voltage. Previously we
have calculated that the Droop Voltage = ILoad * Rdroop,
where Rdroop is the load line slope specified as 0.0021
(V/A) in the Intel IMVP-6 specification. Knowing this
relationship, the overcurrent protection threshold can be set
up as a voltage droop level. Knowing this voltage droop
level, one can program in the appropriate drop across the
Roc resistor. This voltage drop will be referred to as Voc.
Once the droop voltage is greater than Voc, the PWM drives
will turn off and PGOOD will go low.
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OC
FIGURE 48. EQUIVALENT MODEL FOR DROOP AND DIE SENSING USING DISCRETE RESISTOR SENSING
Internal to
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ISL6260
VDIFF
Σ
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
-
+
+
+
For information regarding Intersil Corporation and its products, see www.intersil.com
10uA
RTN
1
1
27
+
+
-
-
DROOP
VSEN
-
+
DROOP
OCSET
VSUM
DFB
VO'
VSUM
ISL6260C
Roc
Voc
VN
VO'
The selection of Roc is given below in Equation 21.
Assuming we desire an overcurrent trip level, Ioc, of 55A,
and knowing from the Intel Specification that the load line
slope, Rdroop is 0.0021 (V/A), we can then calculate for Roc
as shown in Equation 21.
Roc
Note, if the droop load line slope is not -0.0021 (V/A) in the
application, the overcurrent setpoint will differ from
predicted.
A capacitor may be added in parallel with Roc to improve
noise rejection but the Roc*capacitor time constant cannot
exceed 20µs. Do not remove Roc if overcurrent protection is
not desired. The maximum Roc is 30k.
+
-
=
Ioc
------------------------------------ -
Vrsense
×
10μA
Rdroop
RO
RS
EQV
EQV
EQV
=
55
------------------------------ -
=
=
=
10x10
RS
Iout
×
RO
N
N
0.0021
×
–
6
Rsense
=
N
11.5kΩ
March 6, 2009
(EQ. 21)
FN9259.2