Details, datasheet, quote on part number: MC44107P
PartMC44107P
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Features, Applications

The MC44107 remote control transmitter converts a keyboard input into a pulse code modulated signal suitable for infrared transmission to an appropriate receiver. Its large command capacity, 512 commands, makes it highly suited to remote control applications in TV, video, hi­fi, etc. The transmitter is an LSI circuit realized in complementary MOS technology. Binary Coded, 9­Bit PCM Data Word Simple Modulator Requirements One­Pin Reference Oscillator for External Ceramic Resonator Very Low (Maximum 1 µA) Standby Current Consumption Wide Operating Voltage Range: 10 V Operating Temperature Range: 85° C

This document contains information on a product under development. Motorola reserves the right to change or discontinue this product without notice. REV 2 8/95

Parameter Symbol VDD Vin I DC Supply Voltage Value Unit + 12 Input Voltage, All Inputs 0.5 to VDD 2 DC Current Drain per Pin (Except Signal Out and VDD) DC Current Drain (Signal Out and VDD) Storage Temperature Range °C 10 Tstg 150 * Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the limits in the Electrical Characteristics tables or Pin Descriptions section.

This device contains protection circuitry to guard against damage due to high static voltages or electric fields; however, it is advised that precautions be taken to avoid application of voltage higher than maximum rated voltages to this high­impedance circuit. For proper operation it is recommended that Vin and Vout be constrained to the range VSS (Vin or Vout) VDD. Unused inputs must always be tied to an appropriate logic voltage level (e.g., either VSS or VDD).

Characteristic Inputs R1...R8 and PAGE (with Pull­Up) Iin at Vin 1.2 V Iin at Vin 3 V Iin at Vin 2.8 V Iin at Vin 7 V VIH VIL Outputs CB...CH (Open Drain) Ion at Von 1.2 V Ion at Von 3 V Ioff Output DATA VOH at Isource 1.0 mA VOL at Isink 1.0 mA Supply Voltage Standby Current Active Mode Current Oscillator Frequency

The transmitter emits a 9­bit, labelled A (LSB) to I (MSB), binary code able to encode 512 commands organized as 8 pages of 64 commands. All of these commands are user selectable except the last command (511) which is used as an SST, Start/Stop Transmission code. Each bit of the transmitted signal is in the form of a biphase pulse code modulated (PCM) signal, whose coding is shown in Figure 1.

Figure 1. Signal Coding The keyboard can be a simple switch matrix, connected between the eight row inputs to 8) and the seven column outputs (B to H). VSS acts as the eight column line to give the full complement of 64 commands per page. The maximum "ON" resistance of the keyboard must be limited 500 . Page access is accomplished by connecting, by means of a key, the page input to one of the seven column outputs or by leaving the input circuit open. One of the circuit's major features is its low standby current consumption typically less than 1 µA. For this reason the battery may be left continuously in circuit. As soon as a key is selected, the circuit switches to its active mode and enables the oscillator. To allow for accidental activation and/or key bounce, the circuit requires that the key is held for a minimum delay of tkey, which in the case a 500 kHz oscillator is 65.6 ms. After this delay the column/ row/page command, consisting of a string of messages (see

Figure 2), appropriate to the key selected will be transmitted and repeated until the key is released. Any page key required must be selected before, and held during, the selection of the column/row matrix key. If this sequence is not followed, the circuit will default to the appropriate command between 0 and 63. If two or more page keys are accidentally held down, only the first one pressed will be detected. A command consists of several messages. Each command starts with the message 511 (SST) followed by the message appropriate to the key selected. These messages are repeated until the key is released. The final message is always followed by the SST message, 511. Every message consists of a pre­bit, a pre­bit pause, a start­bit, and nine data bits, where the pre­bit and the start­ bit are always logical "1". The pre­bit allows for the set up of the AGC loop in the receiving preamplifier. The truth tables for data bits are given in Tables 1 and 2, while Figure 2 shows the timing relationships between the commands, messages, and modulation. In the event of accidental multi­key operation, the circuit will react in one of three ways, depending on the combination of the keys selected. When two or more keys are connected to the same row input and any column output except A, the command appropriate to the first key selected will be transmitted until that key is released. After the SST code has been transmitted, assuming another key is still selected, the command appropriate to that key will be transmitted. If the other key has been released in the meantime, the circuit will revert to standby. If two keys are selected in the same row with one being connected to column A, any transmission will terminate with the SST code and then the circuit will transmit the command appropriate to the key connected to column A. In the case where two or more keys connected to the same column are selected, the circuit reacts in a normal manner to the first key activated. Upon selection of the second key, the SST code is transmitted and the circuit will revert to the standby mode. Only when the multi­key condition is released and a single key is selected will the circuit resume operation, as previously described.


 

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