FAN5645 Datasheet, PDF (6/10 Pages) Fairchild Semiconductor – Indicator LED Blinker with Single-Wire Interface

RESET and FOLLOW Modes
Reset mode consists of two control pulses, then CTRL goes
LOW for longer than TTIMEOUT. The IC clears all training
registers to zero, then enters STOP (SLEEP) mode.
CTRL
T_CPHIGH
T_TIMEOUT
T_CPLOW
Figure 7. RESET Mode
After the IC goes through RESET mode; if CTRL goes
HIGH again for longer than TDLY, the IC begins Follow
mode, which causes the LED to be turned ON when
CTRL is HIGH. The IC delays turning on the LED after
the rising edge of CTRL by TDLY to determine whether
the CTRL rising edge is to be interpreted as a
command to turn the LED ON or the beginning of a new
set of control pulses. When the CTRL signal goes
LOW, LED current is turned off and the IC enters STOP
(SLEEP) mode. A TCMD2 waiting period, after the last
trailing edge of the CTRL input, is necessary before a
new command can be received and processed.
Note that FOLLOW mode can be entered upon power
up as well, because all registers are cleared on power
up and the device acts as if in RESET mode.
CTRL
LED
TDLY
Figure 8. FOLLOW Mode
Timing
Symbol
TCMD1
TFTPR
TCMD2
TTIMEOUT
TDLY
TCPHIGH
TCPLOW
TON1
TOFF1
TRESTART
Description
Maximum time window in which starting control pulses must be
finished
Time window from first control pulse rising edge to first rising
edge of training pulse
Maximum time window in which ending control pulses must be
finished
Minimum time window CTRL line has to stay LOW after control
pulses to enter and finish RESET mode (starting from the first
rising edge of the control pulse)
Time delay in playback or follow mode b/t rising edge of CTRL
line to when LED turns ON for the first time
Control pulse HIGH width
Control pulse LOW width
LED ON time in Run modes
LED OFF time in Run modes
Over-temperature or over-current fault time in Follow mode
Min.
1.5
4.0
0.95
2
2
1.0
10
Typ.
Max.
0.8
Units
ms
1.7
ms
0.85
ms
ms
1.10
1.45
ms
55
μs
μs
255.0 ms
2550
ms
10
ms
Over-Current, Over-Temperature, and Under-Voltage Faults
An over-current fault occurs if the ISET pin is shorted to
GND or the RSET resistor value is too low. If the resulting
LED current is greater than three times the maximum
programmed output current (60mA), the IC shuts down
its output current and disables the reference voltage
developed on the ISET pin.
An over-temperature fault occurs when the IC exceeds
150°C, which also causes the IC to shut down its output
current and disable the reference voltage developed on
the ISET pin until the IC cools by about 20°C.
on the ISET pin. If a short-circuit or over-temperature
fault occurs during playback modes, playback is retried
when the next playback pulse (TON) comes. If a short-
circuit or over-temperature fault occurs during Follow
mode, the LED turns off for TRESTART, then Follow mode
tries to resume the LED current according to the current
state of the CTRL line.
If an under-voltage fault occurs, the IC turns off the LED
and enters SLEEP mode until the next control pulse
comes, at which point the IC tries to wake up.
If either fault occurs, the IC turns off the output LED
current and disables the reference voltage developed
© 2006 Fairchild Semiconductor Corporation
FAN5645 • Rev. 1.0.0
6
www.fairchildsemi.com