HCS412I MICROCHIP [Microchip Technology], HCS412I Datasheet - Page 7

• Manufacturer Part Number: HCS412I
• Description: KEELOQ Code Hopping Encoder and Transponder
• Manufacturer: MICROCHIP [Microchip Technology]

TABLE 2-2:
FIGURE 2-7:
2.2.6
The HCS412’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.
The low voltage detector result is included in encoder
transmissions (VLOW) allowing the receiver to indicate
when the transmitter battery is low (Figure 3-2).
The HCS412 indicates a low battery condition by
changing the LED operation (Figure 3-9).
NORMALIZED
RF
OSCT3:0
V
2002 Microchip Technology Inc.
DD
0111b
0011b
0010b
0001b
0000b
1111b
1110b
1101b
1000b
TE
Note:
LEGEND
+
-
= 2.0V
= 3.0V
= 6.0V
1.10
1.08
1.06
1.04
1.02
1.00
0.98
0.96
0.94
0.92
0.90
LOW VOLTAGE DETECTOR
-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
Values are for calibrated oscillator.
Fastest Oscillator Setting (short T
Slowest Oscillator Setting (long T
OSCILLATOR CALIBRATION
VALUE (OSCT)
HCS412 NORMALIZED RF
VERSUS TEMP
Temperature °C
Slower (longer T
Faster (shorter T
Nominal Setting
Description
RF
RF
TE
TE
:
:
:
:
:
:
E
E
)
)
TE
E
E
Preliminary
)
)
FIGURE 2-8:
TABLE 2-3:
TABLE 2-4:
2.2.7
The S2/RFEN/LC1 pin may be used as a button input,
RF enable output or as an interface to the LF antenna.
Select between LC1 antenna interface and S2/RFEN
functionality with the button/transponder select (S2LC)
configuration option (Table 2-2).
2.2.7.1
The S2/RFEN/LC1 pin defaults to LF antenna output
LC1 when the HCS412 is first connected to the supply
voltage (i.e., battery replacement).
The configuration register controlling the pin’s function
is loaded on the first device activation after battery
replacement. A desired S2 input state is therefore
enabled only after the first activation of either S0, S1 or
LC0. The transponder bias circuitry switches off and
the internal pull-down resistor is enabled when the S2/
RFEN/LC1 pin reaches button input configuration.
There will be an extra delay the first activation after
connecting to the supply voltage while the HCS412
retrieves the configuration word and configures the
pins accordingly.
VLOWSEL
Volts (V)
VLOW
0
1
0
1
THE S2/RFEN/LC1 PIN
5.0
4.6
4.4
4.2
4.0
3.8
2.8
2.6
2.4
2.2
2.0
1.8
1.6
4.8
S2 BUTTON INPUT CONSIDERATIONS
-40
Nominal V
Nominal
Point
2.2V
4.4V
Trip
V
V
TYPICAL VOLTAGE TRIP
VLOWSEL OPTIONS
POINTS
VLOW STATUS BIT
DD
DD
is above selected trip voltage
is below selected trip voltage
0
LOW
V
V
for 3V battery applications
for 6V battery applications
LOW
LOW
Description
trip point
sel = 0
50
sel = 1
HCS412
Description
85
DS41099C-page 7
V
Temp (°C)
LOW