ISL6336B Datasheet, PDF (23/31 Pages) Intersil Corporation – 6-Phase PWM Controller with Light Load Efficiency Enhancement and Current Monitoring

ISL6336B
VCC
R
TM1
TM
VR_HOT
o_C
R
NTC
0.333V_CC
FIGURE 14. BLOCK DIAGRAM OF THERMAL MONITORING
FUNCTION
100
90
80
70
60
50
40
30
20
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
FIGURE 15. THE RATIO OF TM VOLTAGE TO NTC
TEMPERATURE WITH RECOMMENDED PARTS
TM
0.391*VCC
0.333*VCC
VR_FAN
VR_HOT
TEMPERATURE
t2 t3
FIGURE 16. VR_HOT SIGNAL vs TM VOLTAGE
Based on the NTC temperature characteristics and the
desired threshold of VR_HOT signal, the pull-up resistor
R_TM1 of TM pin is given by Equation 20:
R_TM1 = 2.75xR_NTC(t3)
(EQ. 20)
R_NTC(t3) is the NTC resistance at the VR_HOT threshold
temperature t3.
The NTC resistance at the set point T2 signal can be
calculated as:
R_NTC(t2) = 1.267xR_NTC(t3)
(EQ. 21)
R_NTC(t1) = 1.644xR_NTC(t3)
(EQ. 22)
With the NTC resistance value obtained from Equations 21
and 22, the temperature value t2 and t1 can be found from
the NTC datasheet.
Temperature Compensation
ISL6336B supports inductor DCR sensing, or resistive
sensing techniques. The inductor DCR has a positive
temperature coefficient of about +0.385%/°C. Because the
voltage across inductor is sensed for output current
information, the sensed current has the same positive
temperature coefficient as the inductor DCR.
In order to obtain the correct current information, there
should be a way to correct the temperature impact on the
current sense component. The ISL6336B provides two
methods: integrated temperature compensation and external
temperature compensation.
Integrated Temperature Compensation
When the TCOMP voltage is equal to or greater than V_CC/15,
ISL6336B will utilize the voltage at the TM and TCOMP pins to
compensate the temperature impact on the sensed current.
The block diagram of this function is shown in Figure 17.
V_CC
R _TM1
TM
o_c
R
NTC
V_CC
R
TC1
TCOMP
R _TC2
NON-LINEAR
A/D
I₆
D/A
k_i
CHANNEL
CURRENT
SENSE
I₅ I_{4 I3}
I_Sen6
I_Sen5
I_Sen4
I_Sen3
I_Sen2
I_Sen1
I₂ I₁
4-BIT
A/D
DROOP IOUT AND
OVERCURRENT
PROTECTION
FIGURE 17. BLOCK DIAGRAM OF INTEGRATED
TEMPERATURE COMPENSATION
When the TM NTC is placed close to the current sense
component (inductor), the temperature of the NTC will track
the temperature of the current sense component. Therefore,
the TM voltage can be utilized to obtain temperature of the
current sense component.
23
FN6696.2
August 31, 2010