Datasheet

 2011-2012 Microchip Technology Inc. DS75018C-page 249
dsPIC33FJ06GS001/101A/102A/202A and dsPIC33FJ09GS302
21.0 CONSTANT CURRENT
SOURCE
The constant current source module is a precision
current generator and is used in conjunction with ADC
to measure the resistance of external resistors
connected to device pins.
21.1 Features Overview
The constant current source module offers the following
major features:
• Constant current generator (10 µA nominal)
• Internal selectable connection to one out of four pins
• Enable/disable bit
21.2 Module Description
Figure 21-1 shows a functional block diagram of the
constant current source module. It consists of a
precision current generator with a nominal value of
10 µA. The module can be enabled and disabled using
the ISRCEN bit in the ISRCCON register. The output
of the current generator is internally connected to one
out of up to 4 pins. The OUTSEL<2:0> bits in the
ISRCCON register allow selection of the target pin.
The current source is calibrated during testing.
FIGURE 21-1: CONSTANT CURRENT SOURCE MODULE BLOCK DIAGRAM
Note 1: This data sheet summarizes the features
of the dsPIC33FJ06GS001/101A/102A/
202A and dsPIC33FJ09GS302 families
of devices. It is not intended to be a
comprehensive reference source. To
complement the information in this
data sheet, refer to Section 19.
“Inter-Integrated Circuit (I
2
C™)”
(DS70195) in the “dsPIC33F/PIC24H
Family Reference Manual”, which is
available on the Microchip web site
(www.microchip.com).
2: Some registers and associated bits
described in this section may not be
available on all devices. Refer to
Section 4.0 “Memory Organization” in
this data sheet for device-specific register
and bit information.
ISRC1
ISRC3
M
U
X
OUTSEL<2:0>
ISRC2
ISRC4
ISRCEN
Constant Current Source