U426B Datasheet, PDF (3/6 Pages) TEMIC Semiconductors – INFRARED DRIVER

U426B
Constant Current Driver (DRV)
The constant current driver converts the incoming data
pulses into adequate constant current pulses. A high level
applied to the data input causes a constant current flow
through the IR diode connected to the IRED output. This
current can be programmed via the external resistor (R_S).
To calculate the output current, use the following
formula:
+ I_RED
150
mV
R_S
Power Supply
The power-supply circuit generates the internal supply
voltage from an external voltage (V_S = 2.4 V to 12 V).The
Pin V_S is protected by an internal suppressor diode
against voltages above 13 V. The internal supply voltage
can be switched on/off with a high/low level at the WAKE
input. Setting WAKE to low level switches the circuit
from busy to standby mode which results in a very low
current consumption (2 mA). Every change between busy
and standby mode needs a latency of up to 1 ms. Data
transmission and voltage monitoring only takes place
while WAKE remains high.
Monitoring Comparator (COMP)
The monitoring comparator compares the voltage at Pin
MON-I to an internal reference voltage of V₃ = 525 mV
typ. The open collector output transistor is active if the
voltage at Pin MON-I falls below the internal threshold
voltage. The comparator can be used to monitor the pow-
er-supply battery.
WAKE
internal
circuit state
Standby
t_SB
DATA
Busy
IRED
Output current
MON–I
MON–O
t_d
Figure 4. Timing diagram
Rev. A2, 15-Oct-98
Standby
t_SB
95 9878
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