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ISL6364 Datasheet, PDF (18/44 Pages) Intersil Corporation – Dual 4-Phase + 1-Phase PWM Controller for VR12/IMVP7 Applications
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ISL6364
FIGURE 8. VOLTAGE ACROSS C WITH MATCHING RC
Equation 10 shows that the ratio of the channel current to the
sensed current, ISEN, is driven by the value of the sense resistor
and the RISEN.
ISEN
=
IL
⋅
-R-----S---E---N---
RISEN
(EQ. 10)
Figures 5 and 7 configurations apply for VR1 output, while the
RISEN should include the internal metal impedance of 10.5Ω for
accurate current sense.
For VR0 output, the RISEN resistor of each channel is integrated,
while its value is determined by the RSET resistor. The RSET
resistor value can be from 3.84kΩ to 115.2kΩ and is 64x of the
required ISEN resistor value. Therefore, the current sense gain
resistor (Integrated RISEN) value is effectively set at 60Ω to
1.8kΩ. Figures 9 and 10 show the configurations for inductor
DCR sensing and resistive sensing of VR0, respectively; their
sensing current is represented by Equations 11 and 12,
respectively.
ISEN
=
IL
⋅
D-----C----R-----⋅---6----4--
RSET
(EQ. 11)
ISEN
=
IL
⋅
R-----S---E---N-----⋅---6----4--
RSET
(EQ. 12)
The inductor DCR value will increase as the temperature increases.
Therefore, the sensed current will increase as the temperature of
the current sense element increases. In order to compensate the
temperature effect on the sensed current signal, a Negative
Temperature Coefficient (NTC) resistor can be used for thermal
compensation, or the integrated temperature compensation
function of ISL6364 should be utilized. The integrated temperature
compensation function is described in “Temperature
Compensation” on page 31.
Decoupling capacitor (CT) on ISEN[4:1]- pins are optional and
might be required for long sense traces and a poor layout.
ISL6364
In
IL(s)
L
DCR
INDUCTOR
VL
VC(s)
R
C
VOUT
COUT
CURRENT
SENSE
+
RISEN(n)
-
ISEN
=
IL
D-----C----R-----⋅---6----4--
RSET
ISEN-(n)
ISEN+(n)
RSET
CT, Optional
FIGURE 9. DCR SENSING CONFIGURATION FOR VR0
ISL6364
In
L
R
IL
RSEN ESL
RSENSE
VR
VC(s)
C
VOUT
COUT
CURRENT
SENSE
+
RISEN(n)
-
ISEN
=
IL
R-----S---E---N-----⋅---6----4--
RSET
ISEN-(n)
ISEN+(n)
RSET
CT, Optional
FIGURE 10. SENSE RESISTOR IN SERIES WITH INDUCTORS FOR
VR0
18
FN6861.0
December 22, 2010
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