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7647H–AVR–03/12
Atmel ATmega16/32/64/M1/C1
19. ISRC - Current Source
19.1 Features
• 100µA Constant current source
• ±6% Absolute Accuracy
The ATmega16/32/64/M1/C1 features a 100µA ±5% Current Source. After RESET or up on
request, the current is flowing through an external resistor. The voltage can be measured on the
dedicated pin shared with the ADC. Using a resistor in serie with a ≤≤ 0.5% tolerance is recom-
mended. To protect the device against big values, the ADC must be configured with AVcc as
internal reference to perform the first measurement. Afterwards, another internal reference can
be chosen according 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 19-1. Current Source Block Diagram
AVCC
AREF Internal Circuit
External
Resistor
ISRCEN
AREF / ISRC
100 uA
AREFEN
ADC Input
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