FAN5645 Datasheet, PDF (5/10 Pages) Fairchild Semiconductor – Indicator LED Blinker with Single-Wire Interface

Circuit Description
Operational Modes
At power up, the device is in STOP (“SLEEP”) mode
until a rising edge of a CTRL signal is detected and the
device goes into active mode. Depending upon the
signal applied to CTRL, active mode can be TRAINING,
RUN, RUN ONCE, or FOLLOW AFTER RESET.
Initialization
The reference and the circuit remain in SLEEP mode
until VIN crosses the UVLO threshold and a rising edge
on the CTRL pin is detected. When the IC is in SLEEP
mode, all internal bias circuits are disabled. The training
registers are all reset to 0 at power up.
Training Mode
The IC can record a pattern of up to three distinct HIGH
(TON) and LOW (TOFF) times. These times are recorded
during training in six internal 8-bit counters, one counter
for each distinct TON and TOFF time. If the training pulse
ON or OFF time exceeds the maximum clock counts,
the value is held at the maximum.
TRAINING mode contains the following sequence:
1. Two control pulses, finished within TCMD1. The HIGH
time of the control pulses should be greater than 2µs
and less than 55µs. The LOW time between two
control pulses should be greater than 2µs.
2. CTRL held LOW, for at least TFTPR(MIN), but less than
TFTPR(MAX), measured from the first rising edge of the
control pulse.
3. Between one and three sets of training pulses, where
a training pulse defines the LED’s on time TON and
off-time TOFF.
4. Three control pulses finished within TCMD2 to signify
end of training. The HIGH time of the control pulses
should be greater than 2µs and less than 55µs. The
LOW time between two control pulses should be
greater than 2µs.
5. The IC enters STOP (SLEEP) mode and is able to
receive a new command only after TCMD2 expires.
6. If no end-of-training controls pulses are received after
TOFF3 maximizes out, the IC enters STOP (SLEEP)
mode automatically.
CTRL
T_{C PH IGH}
T_{C PLOW}
T_{FT PR}
T_CMD1
T_ON1
T_OFF1
T_ON2
T_OFF2
T_ON3
Figure 4. TRAINING Mode
T_OFF3
T _CMD2
RUN Mode
When CTRL is raised and held HIGH, and training
registers are not all zeros, repetitive playback of the
trained sequence commences. The delay between
CTRL HIGH and LED on is TDLY1. When CTRL
T DLY
subsequently goes LOW, the IC turns off the LED and
enters STOP (SLEEP) mode. After a TCMD2 time, a new
command can be processed.
CTRL
LED
Trained Sequence
T_ON1
Figure 5. RUN Mode
Run Once Mode
When the IC receives four consecutive control pulses
within TCMD1, followed by CTRL going HIGH after at
least TFTPR(MIN), but less than TFTPR(MAX), the IC plays
T_CPHIGH
T_FTPR
T_CMD1
CTRL
T_CPLOW
back the trained pattern once, then enters STOP
(SLEEP) mode after the trained sequence is completed.
This assumes that training registers are not all zeros.
Trained Sequence
LED
© 2006 Fairchild Semiconductor Corporation
FAN5645 • Rev. 1.0.0
T_ON1
Figure 6. RUN ONCE Mode
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