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ATmega16M1/32M1/64M1 [DATASHEET]
8209E–AVR–11/2012
22. ISRC - current source
22.1
Features
100A constant current source
±2% absolute accuracy
The Atmel ATmega16M1/32M1/64M1 features a 100A ±2% 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 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 according to the previous measured value to refine the result.
When ISRCEN bit is set, the ISRC pin sources 100A. Otherwise this pin keeps its initial function.
Figure 22-1. Current source block diagram.
22.2
Typical applications
22.2.1
LIN current source
During the configuration of a LIN node in a cluster, it may be necessary to attribute dynamically 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 application supported by the
LIN node. A full dynamic node configuration can be used to set-up the LIN nodes in a cluster.
Atmel ATmega16M1/32M1/64M1 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 par-
ticipate in LIN communication.
AVCC
AREF internal circuit
External
resistor
ISRCEN
AREF / ISRC
100uA
AREFEN
ADC input