Texas Instruments TPS40090EVM-002 - Manual (Page 12)

SLUU195 − June 2004
12 TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
With the chosen inductor described in Inductance Value, (section 4.2, of this document) the
following values are used.
•
R=19.6 k
Ω
•
C=10 nF
•
R
NTC
=100 k
Ω
•
R1=124 k
Ω
•
R2=22.6 k
Ω
UDG−03136
R
L
DCR
C
R
L
DCR
C
R2
R1
VOUT
VC
VIN
VDCR VIN
RTHE
RNTC
Figure 6. DCR Current Sensing Circuit with Copper Temperature Compensation
4.7 Overcurrent Limit Protection
The overcurrent function monitors the voltage level separately on each current sense input and
compares it to the voltage on ILIM pin set by the divider from the controller’s reference.
If the threshold of V
ILIM
/2.7 is exceeded, the PWM cycle on the respected phase is terminated.
Voltage level on the ILIM pin is determined by (11).
V
ILIM
+
2.7 I
PH(max)
R
CS
; I
PH(max)
+
I
OUT
)
ǒ
V
IN
*
V
OUT
Ǔ
V
OUT
2 L
OUT
f
SW
V
IN
where
•
I
PH(max)
is the maximum allowable value of the phase current
•
R
CS
is the value of the current sense resistor
(11)