DATA SHEET
BIPOLAR ANALOG INTEGRATED CIRCUITS
µ
PC2800A
PREAMPLIFIER FOR INFRARED REMOTE CONTROL
DESCRIPTION
The
µ
PC2800A is a receiver preamplifier for infrared remote control systems. It can be directly connected
to a PIN photodiode and integrates a high-gain first-stage amplifier, limiter, bandpass filter, detection circuit,
and waveform shaping circuit to provide a receiver preamplifier on a single chip.
FEATURES
• High reliability due to high-frequency lighting fluorescent lamp
Internal trap circuit
• Internal bandpass filter
Central frequency variable by external resistor: f
O
= 30 to 80 kHz
Few variation of central frequency thanks to f
O
trimming
• Low external components
Internal output pull-up resistor and power supply filter resistor
Only low external capacitance required
• ABLC (Automatic Bias Level Control) circuit
Controls fluctuation of bias level cause by disturbance from external light
• Open-collector output
Open-collector output (active low) with pull-up resistor (33 kΩ TYP.)
ORDERING INFORMATION
Part Number
Package
8-pin plastic SOP (225 mil)
µ
PC2800AGR
The information in this document is subject to change without notice.
Document No. S12974EJ6V0DS00 (6th edition)
Date Published October 1998 N CP(K)
Printed in Japan
The mark
shows major revised points.
©
1992
µ
PC2800A
BLOCK DIAGRAM
+
R
2
4
3
C
S
V
CC
f
O
V
CC2
R
S
47
Ω
1
V
CC1
IN+
8
First
stage am-
plifier
Limiter
BPF
+
TRAP
Detection
circuit
R
L
33 kΩ
Wave-
form
shaping
circuit
OUT
2
Output
ABLC
PIN
photodiode
7
R
1
C
2
C
1
IN–
GND
5
C
D
6
PIN CONFIGURATION (Top View)
8-pin plastic SOP (225 mil)
•
µ
PC2800AGR
V
CC1
OUT
V
CC2
f
O
1
2
3
4
8
7
6
5
IN
+
–
IN
C
D
GND
Pin No.
1
2
3
4
5
6
7
8
Symbol
V
CC1
OUT
V
CC2
f
O
GND
C
D
IN
–
IN
+
Pin Name
Power input pin
Output pin
Power output pin
BPF frequency setting pin
Ground pin
Detection capacitor connection pin
First-stage amplifier gain setting pin
Signal input pin
2
µ
PC2800A
1. PIN FUNCTION
Pin
No.
1
Symbol
V
CC1
Pin Name
Power input pin
Internal Equivalent Circuit
Function
Supply a voltage of 5 V
±
10% to this
pin. If the IC malfunctions due to power
noise, connect a bypass capacitor.
V
CC1
An open-collector output pin (active
low) with a pull-up resistor (33 kΩ TYP.)
Connect an external pull-up resistor of
2.2 kΩ or more, if any, to this pin.
2
OUT
Output pin
33 kΩ
2
Output transistor
From waveform
shaping circuit
3
V
CC2
Power output pin
V
CC1
Connect a capacitor of 47
µ
F or so to
this pin to stabilize the supply voltage to
the internal circuit.
3
Internal circuit
power line
4
f
O
BPF frequency
setting pin
4
f
O
setting
block of BPF
Trimming
resistor
Sets the central frequency of the
internal bandpass filter by an external
resistance (refer to
f
O
vs. R
2
Character-
istics
in
CHARACTERISTIC CURVE).
Use a resistor with excellent accuracy
and temperature characteristics.
5
6
GND
C
D
Ground pin
Detection
capacitor
connection pin
Waveform
shaping circuit
GND pin
Connect a smoothing capacitor to this
pin to obtain a DC voltage corresponding
to the output signal level of the internal
bandpass filter.
The 0.01
µ
F is the most suitable value
for the external capacitor between pin 6
and GND. In case of reducing this
capacitor, confirm that the output pulses
from pin 2 have enough width even if
the longest burst signal is inputted.
6
BPF
output signal
3
µ
PC2800A
Pin
No.
7
Symbol
IN
–
Pin Name
First-stage gain
setting pin
Internal Equivalent Circuit
Function
Reverse input pin of the first-stage
amplifier.
Connect a capacitor (0.01
µ
F) to
prevent direct current so that the first-
stage amplifier operates as an AC
amplifier. The gain of the amplifier can
be adjusted by an external resistor (0 to
1 kΩ) (refer to
A
V
vs. R
1
Characteris-
tics
in
CHARACTERISTIC CURVE).
This pin has an internal impedance of
90 kΩ (TYP.) and can be directly
connected to a PIN photodiode.
Because this is the input pin of a high-
sensitivity amplifier, exercise care that
noise is not superimposed on this pin.
Keep the wiring length of the cathode of
the PIN photodiode as short as possi-
ble.
2.5 V
90 kΩ
ABLC
7
8
IN
+
To limiter
circuit
Signal input pin
8
4
µ
PC2800A
2. EXAMPLE OF MEASURES TO PREVENT MALFUNCTIONING DUE TO NOISE
2.1 Radiation noise
• Keep the wiring length between the PIN photodiode and pin 8 as short as possible.
• Keep the signal lines of pins 2 and 6 as far away as possible from those of pins 7 and 8.
• Commonly ground the anode of the PIN photodiode and the external capacitor connected to pin 7.
Separate the GND and power GND of pin 6 from these.
• Cover the entire circuit in a shield case.
2.2 Power noise
• Monitor the noise superimposed on pin 3 with an oscilloscope. If high-frequency noise is superimposed,
connect a ceramic capacitor of 0.1
µ
F or so between pin 3 and GND.
a capacitor between pin 1 and GND.
2.3 External light disturbance noise
• Use a PIN photodiode with an excellent spectral sensitivity.
• Use a PIN photodiode with a lens and with a narrow directional angle.
2.4 Noise
• Insert an external resistor (R
1
: 1 kΩ or less) in series to C
1
between pin 7 and GND to decrease the voltage
gain. In this case, however, the distance is shortened and care must be exercised not to decrease the
voltage gain too much.
If low-frequency noise is
superimposed, increase the capaciance of the capacitor between pin 3 and GND. If necessary, connect
3. NOTICE FOR USE
The
µ
PC2800A is designed for the infrared remote control receivers of audio-visual equipment, air conditioner
and so on. Therefore the
µ
PC2800A may not be suitable for some applications that require accurate pulse widths
such as data communications. In case of using the
µ
PC2800A under the accurate pulse width condition, confirm
that the output pulses from pin 2 have enough accuracy in actual environmental changing (refer to the following
examples).
Example of environmental changing:
Operating ambient temperature, supply voltage, external disturbing light, external noise, input burst
length, input carrier frequency, strength of input light, direction of input light, distance from transmitter,
characteristics of parts (including the
µ
PC2800A) and so on.
5
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