TA31275FN/ TA31275FNG
TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic
TA31275FN, TA31275FNG
AM/FM RF/IF Detector IC for Low Power Wireless System
The TA31275FN is an RF/IF detector IC for AM/FM radio.
The IC incorporates an RF amp, 2-level comparator, and local ×8
circuit
Features
•
•
•
•
•
•
RF frequency: 240 to 450 MHz (multiplication is used)
100 to 450 MHz (multiplication is not used)
IF frequency: 10.7 MHz
Operating voltage range: 2.4 to 5.5 V
Current dissipation: 5.8 mA (FM)/5.4 mA (AM)
(except current at oscillator circuit)
Current dissipation at BS: 0 µA (typ.)
Small package: 24-pin SSOP (0.65 mm pitch)
Weight: 0.09 g (typ.)
Block Diagram
SAW
22
20
19
18
17
16
15
14
13
21
24
23
LPF
LPF
AF
RSSI REF
AM/FM MIX GND1 RF- CHARGE RF-
RF-
OUT IN
OUT
IN
OUT
DEC IN
AM/FM
RSSI
Comparator
×8
OSC-
IN
1
V
CC
-
Lo LoBS
2
3
MIX
OUT
4
IF-
DEC GND2
7
8
Detector
V
CC1
5
IF-IN
6
BS QUAD
9
10
V
CC2
DATA
11
12
BPF
1
03-01-23
TA31275FN/ TA31275FNG
Pin Description
(the values of resistor and capacitor in the internal equivalent circuit are typical.)
Pin No.
Pin Name
Function
Internal Equivalent Circuit
15 kΩ
1
OSC IN
Local oscillator input pin.
1
2 pF
5 kΩ
2
V
CC-Lo
Local’ power supply pin
3
LOBS
Lo switch pin.
H:
×8
circuit pin.
L: Through pass
3
70 kΩ
Mixer output pin.
4
MIX OUT
The output impedance of the pin is typically
330
Ω.
4
245
Ω
5
V
CC1
Power supply pin 1.
6
IF IN
IF amp input pin.
3 kΩ
170
Ω
170
Ω
IF amp input pin.
7
IF DEC
Used as a bias coupling pin.
6
15 kΩ
7
5 kΩ
40 kΩ
8
GND2
GND pin 2.
9
BS
Battery saving pin.
9
5 kΩ
2
03-01-23
TA31275FN/ TA31275FNG
Pin No.
Pin Name
Function
Internal Equivalent Circuit
8 kΩ
2 kΩ
3 kΩ
5 kΩ
10
QUAD
Phase-shift input terminal for the FSK
Demodulator.
Connect to the discriminator or LC.
1 kΩ 1 pF
10
500
Ω
11
V
CC2
Power supply pin 2.
12
DATA
FM/AM waveform shaping output pin.
Open collector output.
Connect a pull-up resistor.
12
13
RF IN
RF signal input pin.
10 kΩ
16
14
RF DEC
Emitter pin for internal transistor.
13
16
RF OUT
RF amp output pin.
14
500
Ω
15
CHARGE
100 kΩ
Control terminal for quick charge circuit.
To use the quick charge circuit, attach a
capacitor.
15
17
GND1
GND pin 1.
2.4 kΩ
18
MIX IN
Mixer input pin.
18
19
AM/FM
Changeover switch for ASK/FSK.
Hi: AM
Lo: FM
300 kΩ
19
500
Ω
8 kΩ
3
03-01-23
TA31275FN/ TA31275FNG
Pin No.
Pin Name
Function
Internal Equivalent Circuit
24
20
REF
Threshold input terminal for 2-level FM/AM
comparator.
23
500
Ω
20
100 kΩ
COMP
DATA
33 kΩ
30 kΩ
30 kΩ
500
Ω
24
100 kΩ
5.5 kΩ
21
RSSI
RSSI output pin.
21
22
AFOUT
Output terminal for FM demodulator.
22
23
LPF IN
FM/AM LPF input pin.
5.5 kΩ
23
24
LPF OUT
FM/AM LPF output pin.
Equivalent circuits are given to help understand design of the external circuits to be connected. They do not
accurately represent the internal circuits.
4
03-01-23
TA31275FN/ TA31275FNG
Functions
1. Waveform Shaper Circuit (comparator)
The output data (pin 12) are inverted.
2. RSSI Function
DC potential corresponding to the input level of IF IN (pin 6) is output to RSSI (pin 21). Output to RSSI
(pin 21) is converted to a voltage by the internal resistance. Thus, connecting external resistance R to pin
21 varies the gradient of the RSSI output as shown below. Note that due to the displacement of
temperature coefficients between external resistor R and the internal IC resistor IC resistor, the
temperature characteristic of the RSSI output may change. Also, the maximum RSSI value should be V
CC
−
1 V or less, because AM doesn’t correct movement Filter AMP when voltage of RSSI high.
30 kΩ
21
R
After R is
connected
IF input level
Figure 1
3. V
CC
Pin and GND Pin
Figure 2
Use the same voltage supply for V
CC
−
Lo (2 pin) and V
CC1
(5 pin) and V
CC2
(11 pin) (or connect them).
Also, use the same voltage supply source for GND1 (17 pin) and GND2 (8 pin) (or connect them).
4. Local Oscillator Circuit
The local oscillator circuit is external-input-only. The device incorporates no transistor for oscillation.
Input to pin 1 at a level from 95 to 105dBµV.
Adjust the values of constants C107 and C108 shown in the application circuit diagram so that the input
level will become approximately 100dBµV.
By switching the Lo switch (LOBS), the frequency set by the external circuit can be used as-is without
using the
×8
circuit.
Lo Switch (LOBS)
Local oscillation
status
H
×8
circuit in operation
L
×8
circuit halted/through pass
5. RF Amp Current Adjustment
The RF amp current dissipation can be regulated by varying resistor R as shown in the figure below.
When R
=
1 kΩ, the current dissipation is approximately 600
µA.
14
RF DEC
Figure 3
R
5
03-01-23
无线连接
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
