ISL6266A_15 Datasheet, PDF (25/31 Pages) Intersil Corporation – Two-phase Core Controllers(Montevina, IMVP-6+)

ISL6266, ISL6266A

where R_{NTCT} is the normalized NTC resistance to its
nominal value. Most data sheets of the NTC thermistor give
the normalized resistor value based on its value at +25°C.
Once the NTC thermistor resistor is determined, the series
resistor can be derived by Equation 14:
R_S = ₆--¹--₀-^.--²-_--^V--_A-- – R_NTCT1 = 20k – R_{NTC_T1}
(EQ. 14)
Once R_NTCTo and R_s is designed, the actual NTC resistance
at T₂ and the actual T₂ temperature can be found in
Equations 15 and 16:
R_{NTC_T2} = 2.96k + R_{NTC_T1}
(EQ. 15)
T_{2_actual} = -_1b------l-_n----_{}----_R---_{R------N--N------T---T}-----_{C--C------_--T----T----o--2-----}--¹--+-----₁-----_---_--₂---₇----₃-----+----_T----_o-----_ – 273
(EQ. 16)
For example, if using Equations 12, 13 and 14 to design a
thermal throttling circuit with the temperature hysteresis
+100°C to +105°C, since T₁ = +105°C and T₂ = +100°C,
and if we use a Panasonic NTC with b = 4700, Equation 12
gives the required NTC nominal resistance as
R_{NTC_To} = 459k.
In fact, the data sheet gives the resistor ratio value at
+100°C to +105°C, which is 0.03956 and 0.03322
respectively. The b value 4700k in the Panasonic data
sheet only covers to +85°C. Therefore, using Equation 13 is
more accurate for +100°C design, the required NTC nominal
resistance at +25°C is 467k. The closest NTC resistor
value from the manufacturer is 467k. The series resistance
is given by Equation 17 as follows:
R_S = 20k – R_{NTC_105C} = 20k – 15.65k = 4.35k
(EQ. 17)
The closest standard resistor to this result is 4.42kThe NTC
resistance at T₂ is given by Equation 18.
R_{NTC_T2} = 2.96k + R_{NTC_T1} = 18.16k
(EQ. 18)
Therefore, the NTC branch is designed to have a 470k
NTC and 4.42k resistor in series. The part number of the
NTC thermistor is ERTJ0EV474J in an 0402 package. The
NTC thermistor should be placed in the spot that provides
the best indication of the voltage regulator circuit
temperature.
Static Mode of Operation - Static Droop Using DCR
Sensing
As previously mentioned, the ISL6266A has a differential
amplifier that provides precision voltage monitoring at the
processor die for both single-phase and two-phase
operation. This enables the ISL6266A to achieve an
accurate load line in accordance with the IMVP-6+
specification.
DESIGN EXAMPLE
The process of compensation for DCR resistance variation
to achieve the desired load line droop has several steps and
may be iterative.
A two-phase solution using DCR sensing is shown in Figure 37.
There are two resistors connecting to the terminals of inductor
of each phase. These are labeled RS and RO. These resistors
are used to obtain the DC voltage drop across each inductor.
The DC current flowing through each inductor will create a DC
voltage drop across the real winding resistance (DCR). This
voltage is proportional to the average inductor current by Ohm’s
Law. When this voltage is summed with the other channel’s DC
voltage, the total DC load current can be derived.
10µA
OC
-
+
INTERNAL TO
ISL6266
+
1
+
-
OCSET
+
DRO-OP
VSUM
DFB
DROOP
VSUM
+
RSEQV = ^R---₂--^S---
VdcrEQV = IOUT  ^D-----^C-₂----^R---
+
-
+
1
+
-
VDIFF
RTN VSEN
VO'
Cn
VN
-
VO'
Rn = -_--_RR-----_nn---_tt--_cc----++-----_RR----_ss---_ee----_rr--_ii-_ee----_ss---_---+^-----^RR-----^pp---^aa---^rr
ROEQV = ^R----₂-^O---
FIGURE 40. EQUIVALENT MODEL FOR DROOP AND DIE SENSING USING DCR SENSING
25
FN6398.4
August 25, 2015