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PT2248 V2.7

- 4 -

June, 2005

Infrared Remote Control Transmitter

PT2248

FUNCTION DESCRIPTION

OSCILLATION CIRCUIT

When the self-bias type amplifier is housed by CMOS inverter method, the oscillation circuit can be

constructed when a ceramic resonator has been connected.

23

C1

C2

Rf

Cer am ic Res on ator

45 5K Hz

C1 , C2 = 120 pF ~ 150p F

When the oscillation frequency is set at 455KHz, the carrier wave of the transmitting signal is set at

38KHz. Unless the keys are being operated, the oscillation is normally stopped; thereby, reducing

power consumption.

KEY INPUT

18 Keys can be connected by Key Inputs K1 ~ K6 and timing signals T1 ~ T3.

Multiple Keying (maximum of 6 keys) is possible for the keys connected to T1 line (Output becomes

continuous pulses).

The order of priority of the timing signal line is T1, T2, and T3. When 2 or more keys that are connected

to T2 (or T3) line are pressed simultaneously, the single output will have the preferential order of K1 ~

K6.

Furthermore, the keys connected to T2 and T3 lines are for single signals and no second signal is

transmitted unless input is made after the key is released once.