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FM IF RECEIVER FOR FLEX PAGER S1T8515A
INTRODUCTION
The S1T8515A is a designed for FM detection on the FLEX pager set.
It consists of an Oscillator, Mixer, Limiting IF Amp. Quadrature
Detector, Regulator, RSSI (Received Signal Strength Indicator), Bit
Rate Filter, and a 2-level / 4-level FSK comparator.
It has a 24-SSOP (0.65mm)Surface Mount Package.
FEATURES
• Internal A/D converter for 4 level FSK (2-bit ADC)
• High transmission rate: 6400bps (Max.)
• Operating voltage range: V
• Typical supply current: 1.5mA at 1.4V
• Low battery detection circuit (alarm function): 1.05V
• Mixer operating frequency: 10 ~ 50MHz
• Package type: 24-SSOP (0.65mm)
= 1.1 ~ 4.0V
CC1
ORDERING INFORMATION
24−SSOP−BD209
Device Package Operating Temperature
S1T8515A01-U0B0 24−SSOP−BD209 −20°C ~ +70°C
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S1T8515A FM IF RECEIVER FOR FLEX PAGER
BLOCK DIAGRAM
MI GND REGO REGC AO FSKO1 FSKO2 BSC QC1 QC2 FSKR2 RSSI
24 23 22 21 20 19 18 17 16 15 14 13
2nd
MIX
X-tal
Osc.
1 2 3 4 5 6 7 8 9
OSCI OSCO MO Vcc LI LD FSKR1 QD C1 C2 C3 FIL VAR
PIN CONFIGURATION
1.0V Regulator Alarm
Limiting IF
Amplifier
1
OSCI
MO
Vcc
LD
2
3
4
5
LI
6
S1T8515A
OSCO
FSK
Comparator
Quad
Detector
24
MI
23
GND
22
REGO
21
REGC
20
AO
19
FSKO1
Quick
Charge
Bit-rate Filter
10 11 12
FSKR1
QD
C1
C2
C3
FIL VAR
10
11
12
7
8
9
18
17
16
15
14
13
FSKO2
BSC
QC1
QC2
FSKR2
RSSI
2
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FM IF RECEIVER FOR FLEX PAGER S1T8515A
PIN DESCRIPTION
Pin No Symbol Description
1 OSCI Oscillator input (Base). The oscillator is an internally biased colpitts type.
2 OSCO Oscillator output (Emitter).
3 MO Mixer output (Output impedance ≈ 1.5kΩ) Connect a 455kHz filter between this pin
and the LI.
4 V
5 LI IF limiter amplifier input (Input impedance ≈ 1.5kΩ).
6 LD Bypass capacitor connect pin for the IF limiter amp.
7 FSKR1 Differential Amp Reference input on the FSK comparator.
8 QD Quadrature detection, phase shiftier input.
9
10
11
12 FIL VAR Bit-rate filter selection.
13 RSSI RSSI output.
14 FSKR2 Differential Amp Reference input on the FSK comparator for 4-Level FSK Detection.
15, 16 QC2, QC1 Quick charge control 2 & 1.
17 BSC Battery saving control.
CC
C1
C2
C3
Power supply voltage.
Capacitors for bit-rate filter.
High: Internal cut-off frequency will be set to Low.
Low: Internal cut- off frequency will be set to High.
The power of received RF signal can be detected by monitoring the limiter amplifier.
High: Quick charge-discharge on. Low: Quick charge-discharge off.
High: Battery saving off-normal mode operation.
Low: Battery saving on-battery save mode operation.
18 FSKO2 The output signal from the Bit-rate filter is compared with FSK Reference signal, and
the final output signal will be output to the LSB after 4-Level FSK detection.
19 FSKO1 The final output signal will be output to the MSB after 4-Level FSK detection.
20 AO Alarm output.
This pin becomes high, when VCC drops below 1.05V.
21 REGC S1T8515A has an internal PNP transistor.
But, it also can support an external PNP transistor to control the power.
22 REGO Regulated voltage output.
23 GND Ground.
24 MI Mixer input (Input impedance ≈ 1.5kΩ).
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S1T8515A FM IF RECEIVER FOR FLEX PAGER
ABSOLUTE MAXIMUM RATINGS
Characteristic Symbol Value Unit
Supply Voltage V
Power Dissipation P
Operating Temperature T
Storage Temperature T
CC (MAX)
D
OPR
STG
4 V
760 mW
−20 — +70 °C
−55 — +125 °C
ELECTRICAL CHARACTERISTICS
(VCC = 1.4V ±5%, fIN (2MIX) = 21.4MHz, f
otherwise specified)
Characteristic Symbol Test Conditions Min. Typ. Max. Unit
Operating current I
Alarm detection voltage V
Alarm low level output voltage V
Alarm high level leakage current I
FSK low level output voltage V
FSK high level leakage current I
Regulator output voltage V
Quick charge current I
Input for −3dB sensitivity V
Recovered audio output voltage V
Mixer conversion gain ∆G
CCN
I
CCS
AD
O (AL)
LKG (AL)
L (FSK)
LKG (FSK)
OREG
C
LIM
O (RAO)
V (M)
Signal to noise ratio S/N V
Total Harmonic Distortion THD V
Mixer 3rd order intercept point 3RD − − −10 − dBm
= ±4.8kHz, f
DEV
= 800Hz, Ta = 25°C, FIL_VAR = “H”, unless
MOD
No Input Signal − 1.5 1.75 mA
Battery Saving − 0 10 µA
− 1.0 1.05 1.1 V
I = 100µA − − 0.4 V
− − − 2 µA
I = 100µA − − 0.4 V
− − − 2 µA
− 0.95 1.0 1.05 V
− 50 70 − µA
Mixer Input − 2.5 7.5 µVrms
V
IN (2MIX)
= 500µVrms 36 54 78 mVrms
Ceramic Filter loss = −1dB 8 12 16 dB
IN (MIX1N)
IN (MIX1N)
= 500µVrms 38 55 − dB
= 500µVrms − 2.0 3.5 %
Mixer input resistance R
Limiting amp input resistance R
I (MIX)
I (LA)
AM rejection ratio AMR V
Data shaping output duty DR V
RSSI output voltage V
RSSI output resistance R
4
RSSI
RSSI
IN (2MIX)
= 500µVrms
(AM = 300%)
IN (2MIX)
V
IN (2MIX)
= 500µVrms 40 50 60 %
= 1mVrms 0.49 0.7 0.91 V
− 3.5 5 6.5 kΩ
− 0.9 1.5 2.1 kΩ
25 40 − dB
− 90 100 110 kΩ
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FM IF RECEIVER FOR FLEX PAGER S1T8515A
TEST CIRCUIT
RF Input
51
1000p
MI GND REGO REGC AO
24 23 22 21 20 19 18 17 16 15 14 13
2nd
MIX
Reg. out
2.2µ
+
1.0V Regulator Alarm
X-tal
Osc.
Alarm out FSKO1 FSKO2
100K
100K
100K
FSKO1 FSKO2
FSK
Comparator
Limiting IF
Amplifier
Vcc QC1 QC2
L H L
BSC QC1 QC2
Quick
Charge
Quad
Detector
1 2 3 4 5 6 7 8 9
OSCI OSCO MO Vcc LI LD FSKR1 QD C1 C2 C3
1000p
3.3K
20.945MHz
56p
39p
CFMW455E
0.1µ
10µ
+
CDBM
455
+
10u
FSKR2 RSSI
+
10µ
FSKR2
RSSI
Bit-rate Filter
10 11 12
1500p
1200p
0.1µ
FIL VAR
LH
5
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S1T8515A FM IF RECEIVER FOR FLEX PAGER
NOTES
6
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