Datasheet

I
OCL(PEAK)
+ V
OCL
1
Rs
Rx ) Rc
Rc
( )
Lx
Cx × Rx//Rc =
Rs
Co
Lx
VIN
Rs(DCR)
+
Cx
Rx
Control
logic
&
Driver
DRVH
DRVL
CSP
CSN
Inductor
Rc
Co
Lx
VIN
Rs(DCR)
+
Cx
Rx
Control
logic
&
Driver
DRVH
DRVL
CSP
CSN
Inductor
TPS51220A
SLUS897E –DECEMBER 2008–REVISED JANUARY 2013 www.ti.com
INDUCTOR DCR CURRENT SENSING
To use inductor DCR as current sensing resistor (Rs), the configuration needs to change as below. However, the
equation that must be satisfied is the same as the one for the resistor sensing.
Figure 48. Inductor DCR Current Sensing
Figure 49. Inductor DCR Current Sensing With Voltage Divider
TPS51220A has fixed V
(OCL)
point (60 mV or 31 mV). In order to adjust for DCR, a voltage divider can be
configured a described in Figure 49.
For Rx, Rc and Cx can be calculated as shown below, and overcurrent limitation value can be calculated as
follows:
(19)
(20)
Figure 50 shows the compensation technique for the temperature drifts of the inductor DCR value. This scheme
assumes the temperature rise at the thermistor (R
NTC
) is directly proportional to the temperature rise at the
inductor.
32 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated
Product Folder Links :TPS51220A