PCINT13 datasheet(199/294 Pages) ATMEL

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199

9219A–RFID–01/11

Atmel ATA5505 [Preliminary]

17. ISRC - Current Source

17.1

Features

• 100µA Constant current source

• ±10% Absolute Accuracy

The Atmel

® AVR® features a 100µA ±10% Current Source. Up on request, the current is flow-

ing through an external resistor. The voltage can be measured on the dedicated pin shared

with the ADC. Using a resistor in series with a

≤ 0.5% tolerance is recommended. To protect

the device against big values, the ADC must be configured with AV

CC as internal reference to

perform the first measurement. Afterwards, another internal reference can be chosen accord-

ing to the previous measured value to refine the result.

When ISRCEN bit is set, the ISRC pin sources 100µA. Otherwise this pin keeps its initial

function.

Figure 17-1. Current Source Block Diagram

17.2

Typical Applications

17.2.1

LIN Current Source

During the configuration of a LIN node in a cluster, it may be necessary to attribute dynami-

cally an unique physical address to every cluster node. The way to do it is not described in the

LIN protocol.

The Current Source offers an excellent solution to associate a physical address to the applica-

tion supported by the LIN node. A full dynamic node configuration can be used to set-up the

LIN nodes in a cluster.

The Atmel AVR proposes to have an external resistor used in conjunction with the Current

Source. The device measures the voltage to the boundaries of the resistance via the Analog to

Digital converter. The resulting voltage defines the physical address that the communication

handler will use when the node will participate in LIN communication.

AVCC

ADC Input

External

Resistor

ISRCEN

ADCn/ ISRC

100 uA

PCINT13 Datasheet(PDF) 199 Page - ATMEL Corporation