TPL0102 datasheet(33/48 Pages) TI2

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TPL0102 Code (Voltage Divider Mode)

Current vs TPL0102 Code (Voltage Divider Mode) per TPL0102 Code (Rhetostat Mode)

120

150

180

210

240

256

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

D003

255 (0xFFh)

252 (0xFCh)

248 (0xF8h)

240 (0xF0h)

208 (0xD0h)

128 (0x80h)

0 (0x00h)

set

LOAD_MAX

set

HW(Resistance)

2 V

1.19 mA

TPL0102

1.2 k

480

1.2 k

W +

set

LOAD

set

HW(Resistance)

2 V

19.76 A

TPL0102

1.2 k

100 k

1.2 k

W +

set

LOAD_MAX

set

HW(Resistance)

2 V

1.33 mA

TPL0102

1.2 k

300

1.2 k

W +

TPL0102

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SLIS134C – MARCH 2011 – REVISED SEPTEMBER 2015

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Based upon the voltage divider formula between the setting of the TPL0102 and the 150 k

Ω resistor, the voltage

at the positive input of the OPA317, Vset, can range from 0 to 2 V. This leaves a maximum of 3 V of voltage drop

from the positive side to the negative side of the external load with a 5 V supply. A 1.2 k

Ω resistor is placed in

series with the TPL0102 span setting potentiometer (Rset). At full scale of the span setting potentiometer and the

maximum voltage at Vset (2 V), the maximum value for ILOAD is:

(14)

When the span setting potentiometer is at zero scale with the maximum voltage at Vset, the maximum value for

ILOAD is:

(15)

The same calculations can be made when the potentiometer in voltage divider mode is a zero scale. At zero

scale, Vset will be almost negligible, resulting in 0 A of current no matter the value of the span setting

potentiometer.

8.2.3.2.1

Compensation Components

This design requires a few compensation components to stabilize the feedback network. These include the 1 nF

capacitor and the 200

Ω and 10 kΩ resistors, which were selected based upon the TIPD102 reference design.

8.2.3.3 Application Curves

As the TPL0102 in rheostat mode (span setting potentiometer) moves from zero-scale to full-scale, a new step

(line) is created with a larger achievable maximum current. The rheostat mode potentiometer directly

corresponds to Rset in Equation 13. The TPL0102 in voltage divider mode produces the granular current values

between the minimum and maximum range. The voltage divider potentiometer directly corresponds to Vset in

Equation 13. For example, when the potentiometer in rheostat mode is at code 256, the potentiometer in voltage

divider mode produces a theoretical maximum current of 1.33 mA at code 256 and a minimum current of 0 µA at

code 0.

The current sink does not reach the full 1.33 mA because of the error in resistance of the span setting

potentiometer. At full-scale, the resistor had an actual resistance of 480

Ω.

(16)

Figure 36. Current vs Span Setting Code

TPL0102 Datasheet(PDF) 33 Page - Texas Instruments

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