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TEMIC Semiconductors
TEMIC Semiconductors

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U2532B Datasheet

IR Transmitter and Receiver

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IR Transmitter and Receiver
U2532B
Description
The IC U2532B is a complete IR-Transmitter-Receiver
IC according to the new IrDA 1.0 standard.
ASK-modulation is also possible. Only an external
PIN-photodiode and an infrared emitting diode with
current limiting resistor must be connected to the
corresponding pins. The amplifier with Schmitt-Trigger
formed output signal and the IR-driver need no further
external components. The IC allows data rates from
2.4 kbit/s to 115.2 kbit/s and up to 500 kHz for
ASK-modulation. Two different sensitivity modes, which
can be programmed by applying a “High” or “Low”
voltage at pin SC, ensure either an increase in
transmission distance or a bit error rate of 1E-9. An
internal AGC allows proper operation under EMI
conditions.
Features
D Data rates up to 115.2 kbit/s
D Wide supply voltage range (3 to 5.5 V)
D AGC for EMI immunity
D AGC reset
D High and low sensitivity mode
D BER < 1E-9 in the low sensitivity mode
D Power-On reset
Applications
D IR data transmission
D Compatible to IrDA
D Bidirectional IR data transmission
D Ability to receive ASK modulation
Case: SO16
TxD Driver
V CC
RL
Amp
(AGC)
ST
RxD
SC Reset
95 10210
Figure 1.
TELEFUNKEN Semiconductors
Rev. A1, 27-Sep-96
Preliminary Information
1 (10)




TEMIC Semiconductors
TEMIC Semiconductors

U2532B Datasheet Preview

U2532B Datasheet

IR Transmitter and Receiver

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U2532B pdf
U2532B
Pin Description
P_GND 1
16 NC
TxD 2
RxD 3
15 IRED
14 O_GND
Reset 4
VCC 5
13 NC
U2532B
12 NC
SC 6
11 A_GND
NC 7
10 NC
NC 8
9 IN
95 10244
Figure 2. Pinning
Block Diagram
Pin
1
2
3
4
5
6
7, 8,
10, 12,
13, 16
9
11
14
15
Symbol
P_GND
TxD
RxD
Reset
VCC
SC
NC
Function
Power ground
Transmitter input
Receiver output
AGC-Reset
Supply voltage
Sensitivity Control
Not connected
IN
A_GND
O_GND
IRED
Photodiode input
Analog ground
Output ground
IR-Emitter
2
BIAS
9
TIA
5 15
CGA
AGC
64
Figure 3. Block diagram
DRV
COMP
+
11
1
3
14
95 10211
2 (10)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A1, 27-Sep-96




TEMIC Semiconductors
TEMIC Semiconductors

U2532B Datasheet Preview

U2532B Datasheet

IR Transmitter and Receiver

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U2532B pdf
U2532B
Functionality of the Various Circuit Blocks
Transimpedance Amplifier (TIA)
The input stage provides the necessary bias voltage for the
photodiode and ensures decoupling of the useful signal.
This involves processing the dc and ac portions in sepa-
rate parts of the circuit, BIAS (Bias voltage) and TIA. The
BIAS circuit separates the dc part (sunlight, incandescent
light) from the input signal. The ac portion of the input
current is fed to an inverting amplifier with a sufficiently
low input impedance (TIA). The TIA prevents the signal
slopes to be negatively affected by the junction capaci-
tance of the photodiode.
Controlled Gain Amplifier (CGA)
The CGA consists of two differential amplifiers. The total
gain is 17 in the high sense mode (Sensitivity Control In-
put “High”) and can be reduced to 8 if the Sensitivity
Control Input is set to “Low”. In the low sense mode a
BER of 1E-9 is guaranteed. In the high sense mode
eventually generated output pulses must be suppressed by
software handling. The lower and upper cut-off frequen-
cies of the amplifier are 25 kHz and 900 kHz
respectively. Additionally the overall gain can be
attenuated by 30 dB in 2 dB steps. The attenuation is digi-
tally controlled by the AGC (Automatic Gain Control)
circuit.
Comparator (COMP)
to a value where a BER < 1E-9 is still guaranteed, but sig-
nals from disturbers can be effectively suppressed. With
this feature a proper data transmission can be maintained
also in the presence of energy saving lamps and ceiling
lamps that are common in offices. The dynamic range of
the AGC is max. 30 dB. This provides the ability to sup-
press also strong disturbers. As the AGC acts when the
input signal increases, the transmission distance is re-
duced if disturbances have to be suppressed. The AGC is
digitally controlled and therefore not dependent on any
time constant. The amplification of the CGA is set at ev-
ery input pulse or input burst for ASK-modulation and is
maintained until the next input signal is detected. The sig-
nal strength determines whether to reduce, increase or
maintain the gain. If no input signal is detected in 18 ms,
the AGC considers the data transmission to be finished
and increases the gain by a 2 dB step. Within every 18 ms
the gain is increased by an additional 2 dB step, until the
maximum gain of the CGA is reached. If a “High” signal
is applied at the reset (Pin 4), the AGC is set to maximum
sensitivity. Incoming signals don‘t influence the AGC.
Under this biasing condition it is possible to get maximum
transmission distance also in the presence of a known
strong disturber, if of course the signals of the disturber
can be succesfully suppressed by software handling in the
microprocessor. During “Power-On” the AGC is set to
maximum sensitivity. The gain of the AGC is maintained
while the transceiver is transmitting.
The comparator compares the output signal of the CGA
to an internal threshold voltage. The output of that
comparator is directly connected to an collector output
stage. An internal pull up resistor of 20 kW is provided.
Automatic Gain Control (AGC)
The AGC adjusts the sensitivity of the receiver according
to the strength of the incoming signals. When the input
signal increases, the amplification of the CGA is reduced
Transmitter
IRED Driver (DRV)
The IRED driver DRV is also monolithically integrated
on the transceiver chip providing a high impedance input
to drive a fast IR emitter diode. The “active high” input
signal drives the output stage. This stage mainly consists
of an input amplifier and an open collector NPN transistor
that is saturation controlled. The output transistor is capa-
ble of driving a lood current up to 1 A.
TELEFUNKEN Semiconductors
Rev. A1, 27-Sep-96
Preliminary Information
3 (10)




Part Number U2532B
Description IR Transmitter and Receiver
Maker TEMIC Semiconductors
Total Page 10 Pages
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