HCS370SL MICROCHIP [Microchip Technology], HCS370SL Datasheet - Page 16

• Manufacturer Part Number: HCS370SL
• Description: KEELOQ Code Hopping Encoder
• Manufacturer: MICROCHIP [Microchip Technology]

HCS370
5.0
5.1
The HCS370 has an onboard RC oscillator that con-
trols all the logic output timing characteristics. The
oscillator frequency varies over temperature and volt-
age variances, but stays within ±10% of the tuned
value. All the timing values specified in this document
are subject to this oscillator variation.
FIGURE 5-1:
5.3
The LED pin will be driven low while the HCS370 is
transmitting data. The LED On Time (T
selected between 50 ms and 100 ms with the LED On
Time Select (LEDOS) configuration option. The LED
Off Time (T
voltage drops below the selected V
LED will not blink unless the LED Blink (LEDBL) option
DS41111D-page 16
SPECIAL FEATURES
Internal RC Oscillator
LED Output
ASK RFEN
FSK RFEN
ASK DATA
FSK DATA
LEDOFF
SLEEP
STEP
S0
ASK/FSK INTERFACE
) is fixed at 500 ms. When the V
T
PU
CODE WORD
CODE WORD
T
PLL
LOW
LEDON
trip point, the
) can be
T
Preliminary
G
DD
CODE WORD
CODE WORD
5.2
The RFEN pin will be driven high whenever data is
transmitted through the DATA pin.
The RFEN and DATA outputs also interface with RF
PLL’s. The PLL Interface Select (PLLSEL) configura-
tion option selects between ASK and FSK interfaces.
Figure 5-1 shows the startup sequence for both ASK
and FSK interface options. The RFEN signal will go low
at the end of the last code word, including the guard
time (T
time plus the step-up regulator ramp up delay if the
Wait For Step-Up Regulator (WAIT) configuration
option is a ‘1’. The PLL step-up time (T
to update the EEPROM counter.
is set. If LEDBL is set and V
only flash once. Waveforms of the LED behavior are
shown in Figure 5-2.
For circuits with V
limit the LED circuit with a series resistor. The LED out-
put can safely sink up to 25 mA but adding an external
resistor will conserve battery power. This is an open
drain output but it does have a weak pull-up capable of
driving a CMOS input.
G
T
E
). The power-up time (T
RF Enable and PLL Interface
DD
Wait 2 seconds for next
button if QUEN=1
greater than 3 volts, be sure to
2002 Microchip Technology Inc.
DD
is low, then the LED will
PU
) is the debounce
PLL
) is also used
V
V
REG
BAT