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DS2890

8 of 28

Figure 6. Variable Resistor Configurations

(TO92 Package)

WIPER

VDD

1-WIRE

GND

2.8V to 6.0V

No Connect

2.8V to 6.0V

Bus

Master

1-WIRE

GND

2.8V to 6.0V

Bus

Master

WIPER RESISTANCECONSIDERATIONS

A simplified diagram of the DS2890 resistor array for the potentiometer configuration is shown in

FIGURE 8. In this figure the

resistance of the wiper transistors in Figure 1 are modeled as wiper

resistance R

WIPER

. The value of R

WIPER

varies with device configuration, operational state, and wiper

terminal voltage. Wiper resistance is significantly reduced when an external VDD supply is used and the

device charge pump is enabled. A wiper resistance graph with the charge pump enabled is shown in

FIGURE 10.

FIGURE 8. Potentiometer Resistor Model

WIPER

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 27 28

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