2002 Microchip Technology Inc.
Preliminary
DS41111D-page 5
HCS370
2.0
DEVICE DESCRIPTION
As shown in the typical application circuits (Figure 2-1),
the HCS370 is an easy device to use. It requires only
the addition of buttons and RF circuitry for use as the
encoder in your security application. A description of
each pin is described in Table 2-1. Refer to Figure 2-3
for information on the I/O pins.
TABLE 2-1:
PIN DESCRIPTIONS
The HCS370 will normally be in a low power SLEEP
mode. When a button input is taken high, the device will
wake-up, start the step-up regulator, and go through
the button debounce delay of T
DB
before the button
code is latched. In addition, the device will then read
the configuration options. Depending on the configura-
tion options and the button code, the device will deter-
mine what the data and modulation format will be for
the transmission. The transmission will consist of a
stream of code words and will be transmitted T
PU
after
the button is pressed for as long as the buttons are held
down or until a time-out occurs. The code word format
can be either a code hopping format or a seed format.
The time-out time can be selected with the Time-out
Select (TSEL) configuration option. This option allows
the time-out to be set to 0.8s, 3.2s, 12.8s, or 25.6s.
When a time-out occurs, the device will go into SLEEP
mode to protect the battery from draining when a button
gets stuck. This option must be chosen to meet maxi-
mum transmission length regulatory limits which vary
by country.
FIGURE 2-1:
Figure 2-1(A)
TYPICAL CIRCUITS
Note:
S0-S5 and SHIFT inputs have pull-down
resistors. V
IN
should be tied high if the
step-up regulator is not used.
Name
Pin
Number
Description
S0
S1
S2
S3
S4
1
2
3
4
5
6
Switch input S0
Switch input S1
Switch input S2
Switch input S3
Switch input S4
Switch input S5, or SLEEP
output
SHIFT input
Step-up regulator input
Step-up pulses output
RF enable output
Ground reference
Transmission output pin
Open drain output for LED
with pull-up resistor
Positive supply voltage
S5/SLEEP
SHIFT
V
IN
STEP
RFEN
V
SS
DATA
LED
7
8
9
10
11
12
13
V
DD
14
S2
V
DD
B0
Tx out
Six Button remote with PLL control
B1
S0
S1
S3
LED
V
DD
DATA
V
SS
S4
S5
SHIFT
RFEN
STEP
V
IN
B2
B3
B4
B5
R
LED
RF PLL
D
ATA
I
N
E
NABLE
V
DD
S2
2.05-5.5V
Tx out
Two Button remote with Step-up circuit
Note:
Using SLEEP output low instead of grounding the resistor
divider reduces battery drain between transmissions
S0
S1
S3
LED
V
DD
DATA
V
SS
S4
SLEEP
SHIFT
RFEN
STEP
V
IN
33k
10k
Figure 2-1(B)
2.2 k
330
μ
H
1N4148
C
OUT
22
F
2N3904
6V@1 mA
V
DD
Tx out
Tx1
Tx2
DUAL Transmitter remote control
S2
S0
S1
S3
LED
V
DD
DATA
V
SS
S4
S5
SHIFT
RFEN
STEP
V
IN
Figure 2-1(C)
R
LED
V
DD
1000 pF