HCS473_13 Datasheet, PDF (9/68 Pages) Microchip Technology – KEELOQ® 3-Axis Transcoder

2.3.5 INTERNAL RC OSCILLATOR
The HCS473 runs on an internal RC oscillator. The
internal oscillator may vary ±10% over the device’s
rated voltage and temperature range for commercial
temperature devices. A certain percentage of indus-
trial temperature devices vary further on the slow side,
-20%, when used at higher voltages (VDD > 3.5V) and
cold temperature. The LF and RF communication
timing values are subject to these variations.
2.3.6 LOW VOLTAGE DETECTOR
The HCS473’s battery voltage detector detects when
the supply voltage drops below a predetermined value.
The value is selected by the Low Voltage Trip Point
Select (VLOWSEL) configuration option (Section 3.3).
The low voltage detector result is included in encoder
transmissions (VLOW) allowing the receiver to indicate
when the transmitter battery is low (Section 3.1.4.6).
The HCS473 also indicates a low battery condition by
changing the LED operation (Section 3.1.5).
2.3.7 THE S3/RFEN PIN
The S3/RFEN pin may be used as a button input or RF
enable output to a compatible PLL. Select between S3
button input and RFEN functionality with the RFEN
configuration option (Table 2-2).
TABLE 2-2: RFEN OPTION
RFEN
Resulting S3/RFEN Configuration
0
S3 button input pin with Schmitt Trigger
detector and internal pull-down resistor.
1
RFEN output driver.
S3 may not be used as a button input if the
RFEN option is enabled
HCS473
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Preliminary
DS40035D-page 9