HCS473-I/SL Microchip Technology, HCS473-I/SL Datasheet - Page 19

• Manufacturer Part Number: HCS473-I/SL
• Description: IC KEELOQ 3AXIS TRANSCODR 14SOIC
• Manufacturer: Microchip Technology
• Series: KEELOQ®r
• Type: Code Hopping Encoder and Transponderr

Specifications of HCS473-I/SL

• Applications: Access Control Systems
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.1.4.14
The guard time (T
between consecutive code words when no data is
transmitted. The guard time may be selected in conjuc-
tion with the RF baud rate and preamble duty cycle to
control time-averaged power output for transmitter cer-
tification.
GSEL options:
• 3 RF
• 6.4 ms
• 51.2 ms
• 102.4 ms
3.1.4.15
The Minimum Code Words (MTX) configuration option
determines the minimum number of code words trans-
mitted when a momentary switch input is taken high for
more than T
MTX options:
• 1 code word
• 2 code words
• 4 code words
• 8 code words
3.1.4.16
The HCS473’s Timeout function prevents battery drain
should a switch input remain high (stuck button) longer
than the selectable TSEL time. After the TSEL time, the
device will return to Low-power mode.
The device will stop transmitting in Low-power mode
but there will be leakage across the stuck button input’s
internal pull-down resistor. The current draw will there-
fore be higher than if no button were stuck.
TSEL options:
• 4s
• 8s
• 16s
• 32s
3.1.4.17
Enabling the Long Preamble configuration option
extends the first code word’s preamble to a ‘long’ pre-
amble time LPRL
wake and bias before the data bits arrive. The longer
preamble will be a square wave at the selected RFT
Subsequent code words begin with the standard pre-
amble length.
LPRE options:
• Standard 16 high pulse preamble
• Long preamble, duration defined by LPRL
 2002 Microchip Technology Inc.
TE
PU
Guard Time Select (GSEL)
Minimum Code Words (MTX)
Timeout Select (TSEL)
Long Preamble Enable (LPRE)
, or when a proximity activation occurs.
;
G
) select option determines the time
allowing the receiver more time to
Preliminary
E
.
3.1.4.18
The long preamble length option selects the first code
word’s preamble length when the long preamble option
(LPRE) is enabled. Only the first code word begins with
the long preamble, subsequent code words begin with
the standard 16 high pulses preamble.
LPRL options:
• 75 ms
• 100 ms
3.1.4.19
The preamble duty cycle can be set to either 33% or
50% to limit the average power transmitted, Figure 3-7.
PRD options:
• 50% Duty Cycle
• 33% Duty Cycle
FIGURE 3-7:
3.1.5
The LED pin output varies depending on whether the
device V
below V
The LED pin will periodically be driven low as long as
the device is transmitting and the battery is good. If the
supply voltage drops below the specified V
point, the LED pin will be driven low only once for any
given device activation so long as the low battery con-
dition remains (Figure 3-8). If the battery voltage recov-
ers during the transmission, the LED will begin blinking
again.
50% Duty Cycle
33% Duty Cycle
LOWSEL
DD
is greater than V
LED OPERATION
Long Preamble Length (LPRL)
Preamble Duty Cycle (PRD)
(a flat battery).
T
T
E
E
T
PREAMBLE FORMATS
E
2T
E
LOWSEL
HCS473
(a good battery) or
DS40035C-page 17
LOWSEL
trip