U2538B ATMEL | Alldatasheet
Document overview
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Technical content
Features
- Few External Components Low Power Consumption Microcomputer Compatible Insensitive to Ambient Light and Other Continuous Interferences
Applications
Keyless Entry Systems Remote Control Wireless Data Transfer up to 4 kbit/s
Description
The IC U2538B is a complete IR receiver for data communication. The useful input signals are separated by a special input circuit and amplified by a gain-controlled amplifier. The bandpass filter suppresses the off-band signals. The signal detector, consisting of a demodulator, an integrator and a Schmitt trigger, forms the input signal to an output pulse that can be interfaced to a microcomputer. The AGC and the ATC circuit control the receiver's sensitivity, making it insensitive to ambient light sources. Figure 1. Block Diagram with Typical Circuit
2 U2538B
4717A–IRRC–05/03 Block Diagram &Vth Comp 1 Comp 2 ATC DEM BPF AGC BIAS IN AGND DGND TIA CGA INT ST OUT VS 100 k/g87 VS RF0 RF CAGC dt CAGC TIA Transimpedance amplifier ATC Automatic threshold control CGA Controlled gain amplifier DEM Demodulator BPF Bandpass filter INT Integrator AGC Automatic gain control ST Schmitt trigger
Figure 2. Pinning SO8
1 VS Supply voltage
2 CAGC AGC capacitor
3 OUT Data output
4 DGND GND - DEM/INT/ST
5 IN Input pin diode
6 AGND GND amplifier
7 RF Frequency determination
8 NC Not connected
4 U2538B
signal will be lost due to the junction capacitance of the photodiode. tive coupling of the individual stages. The cut-off frequency is approximately 20 kHz. Figure 3. Characteristic of the Bandpass Filter
twice as much as the minimum detectable signal intensity. Figure 4. Duty Cycle put free of short-time interference. The integrator drives the output stage after being processed through a Schmitt trigger. The internal pull-up resistor can replace an external resistor in some applications.
6 U2538B
4717A–IRRC–05/03 Absolute Maximum Ratings Parameters Symbol Value Unit Supply voltage Pin 1 V S -0.3 to +6.0 V Input voltages Pin 2, 3, and 5 Pin 7 VIN -0.3 to VS -0.3 to +1.5 V Input current Pin 7 I IN 0 to 0.1 mA Power dissipation Tamb = 105/g176CP tot 110 mW Junction temperature T j 125 /g176C Ambient temperature T amb -40 to +105 /g176C Storage temperature T stg -40 to +125 /g176C Thermal Resistance Parameters Symbol Value Unit Junction ambient R thJA 180 K/W
Electrical Characteristics
Tamb = 25°C, VS = 5 V Parameters Test Conditions Symbol Min. Typ. Max. Unit Supply voltage Pin 1 V S 4.5 5.5 V Supply current Pin 1 I S 0.35 0.65 mA Maximum input current VIN = 0 Pin 5 I IN 0.6 mA Output voltage low: IOL = 2 mA Pin 3 V OL 0.2 V Internal pull-up resistor Pin 3 R L 75 100 125 k /g87 Center frequency of bandpass RF = 240 k f0 33.3 35 36.7 kHz Q factor Q7 Freqency range f 20 60 kHz AGC current source sink Pin 2 90 120 100 155 140 nA nA AGC slope Pin 2 20 dB/V Number of pulses required 6 Sensitivity Pin 5 0.7 nA(rms) Switch-on delay, i IN = 0.7 nA (rms) Pin 3, see Figure 5 t don 37 . 5 P e r i o d Switch-off delay, iIN = 0.7 nA (rms) Pin 3, see Figure 5 t doff 51 0 P e r i o d Pulse width, iIN = 0.7 nA (rms), 6p u l s eb u r s t s Pin 3, see Figure 5 t po 4.5 10 Period RfO(k/g87/g418855
8 U2538B
4717A–IRRC–05/03
Package Information
Ordering Information
Extended Type Number Package Remarks U2538B-MFP SO8 Tube U2538B-MFPG3 SO8 Taped and reeled technical drawings according to DIN specifications Dimensions in mm 5.00 4.85 0.4 1.27 3.81 1.4 0.25 0.10 5.2 4.8 3.7 3.8 6.15 5.85 0.2
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