LC72121V-TLM-E [ONSEMI]
PLL Frequency Synthesizer for Electronic Tuning;
| 型号： | LC72121V-TLM-E |
| 厂家： | 
ONSEMI |
| 描述： | PLL Frequency Synthesizer for Electronic Tuning 光电二极管 |
| 文件： | 总27页 (文件大小：1081K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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LC72121, LC72121M, LC72121V
PLL Frequency Synthesizer
for Electronic Tuning
Overview
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The LC72121, LC72121M and LC72121V are high input sensitivity (20
mVrms at 130 MHz) PLL frequency synthesizers for 3 V systems.
These ICs are serial data (CCB*) compatible with the LC72131, and
feature the improved input sensitivity and lower spurious radiation
(provided by a redesigned ground system) required in high-performance
AM/FM tuners.
Functions
High-speed programmable divider
— FMIN: 10 to 160 MHz ... Pulse swallower technique
(With built-in divide-by-2 prescaler)
— AMIN: 2 to 40 MHz ... Pulse swallower technique
0.5 to 10 MHz ... Direct division technique
IF counter
PDIP22 / DIP22S (300 mil)
[LC72121]
— IFIN: 0.4 to 15 MHz ... For AM and FM IF counting
Reference frequency
— One of 12 reference frequencies can be selected
(using a 4.5 or 7.2 MHz crystal element)
1, 3, 5, 9, 10, 3.125, 6.25, 12.5, 15, 25, 50, and 100 kHz
Phase comparator
SOIC24 W / MFP24S (300 mil)
[LC72121M]
— Supports dead zone control.
— Built-in unlocked state detection circuit
— Built-in deadlock clear circuit
An MOS transistor for an active low-pass filter is built in
I/O ports
— Output-only ports: 4 pins
— I/O ports: 2 pins
— Supports the output of a clock time base signal
Operating ranges
— Supply voltage: 2.7 to 3.6 V
SSOP24 (275mil)
[LC72121V]
— Operating temperature: – 40 to 85°C
Package
— DIP22S, MFP24S, SSOP24
* Computer Control Bus (CCB) is an ON Semiconductor’s original bus format and
the bus addresses are controlled by ON Semiconductor.
ORDERING INFORMATION
See detailed ordering and shipping information on page 26 of this data sheet.
© Semiconductor Components Industries, LLC, 2017
July 2017 - Rev. 1
1
Publication Order Number :
LC72121_M_V/D
LC72121, LC72121M, LC72121V
Comparison with the LC72131/M
— Serial data compatible (CCB)
— Identical pin functions
— Two VSS pins were added
— The DIP version is pin compatible
(VSS pins were inserted as the DIP22S NC pins)
— The MFP product provides a modified pin assignment
(The MFP20 package was replaced by an MFP24 package, and extra VSS pins were added)
— The SSOP24 is a newly developed package that has the same pin assignment as the MFP24S product
Pin Assignment
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2
LC72121, LC72121M, LC72121V
Block Diagram
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3
LC72121, LC72121M, LC72121V
Specifications
Absolute Maximum Ratings at Ta = 25°C, V
= V = 0 V
= V
SSd
SSa SSX
Parameter
Maximum supply voltage
Symbol
max
Conditions
Ratings
Unit
V
V
V
DD
–0.3 to +7.0
–0.3 to +7.0
DD
V
IN
V
IN
V
IN
1 max CE, DI, CL, AIN
2 max XIN, FMIN, AMIN, IFIN
3 max IO1, IO2
V
Maximum input voltage
–0.3 to V +0.3
DD
V
–0.3 to +15
–0.3 to +7.0
V
V 1 max DO
O
V
Maximum output voltage
Maximum output current
Allowable power dissipation
V 2 max XOUT, PD
–0.3 to V +0.3
DD
V
O
V 3 max BO1 to BO4, IO1, IO2, AOUT
O
–0.3 to +15
0 to +6.0
0 to +10.0
350
V
I 1 max
O
DO, AOUT
mA
mA
mW
mW
mW
°C
°C
I 2 max
O
BO1 to BO4, IO1, IO2
DIP22S:
MFP24S:
SSOP24:
Pd max
(Ta 85°C)
200
150
Operating temperature
Storage temperature
Topr
Tstg
–40 to +85
–55 to +125
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality should not be assumed,
damage may occur and reliability may be affected.
Allowable Operating Ranges at Ta = – 40 to +85°C, V
SSd
= V
SSa
= V = 0 V
SSX
Ratings
typ
Parameter
Symbol
Conditions
Unit
min
2.7
max
3.6
Supply voltage
V
V
V
V
DD
DD
V 1
IH
V 2
IH
CE, DI, CL
IO1, IO2
0.7 V
0.7 V
6.5
13
DD
Input high-level voltage
Input low-level voltage
Output voltage
V
DD
0
V
CE, DI, CL, IO1, IO2
DO
0.3 V
V
IL
DD
V 1
O
0
0
6.5
V
V 2
O
BO1 to BO4, IO1, IO2, AOUT
13
8
V
f 1
IN
f 2
IN
f 3
IN
f 4
IN
f 5
IN
XIN: V
1
1
MHz
MHz
MHz
MHz
MHz
mVrms
mVrms
mVrms
mVrms
mVrms
mVrms
mVrms
MHz
IN
FMIN: V
2
10
2
160
40
IN
Input frequency
AMIN (SNS = 1): V
AMIN (SNS = 0): V
3
4
IN
0.5
0.4
200
20
40
40
40
40
70
4
10
IN
IFIN: V
5
IN
15
V
1
IN
XIN: f
1
IN
800
800
800
800
800
800
800
8
V
2-1
IN
2-2
IN
FMIN: f = 10 to 130 MHz
FMIN: f = 130 to 160 MHz
V
Input amplitude
V
3
IN
4
IN
AMIN (SNS = 1): f
AMIN (SNS = 0): f
3
IN
4
IN
V
V
5-1
IN
5-2
IN
IFIN: f 5, IFS = 1
IN
V
IFIN: f 5, IFS = 0
IN
Guaranteed crystal oscillator frequency
Xtal
XIN, XOUT: *
Note: Recommended value for CI for the crystal oscillator element: CI 120 (4.5MHz), CI 70 (7.2MHz)
Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond the Recommended
Operating Ranges limits may affect device reliability.
Electrical Characteristics in the Allowable Operating Ranges
Ratings
Parameter
Internal feedback resistance
Internal pull-down resistance
Symbol
Conditions
Unit
min
typ
max
Rf1
Rf2
XIN
1
M
k
k
k
k
k
V
FMIN
AMIN
IFIN
500
500
250
200
200
Rf3
Rf4
Rpd1
Rpd2
FMIN
AMIN
CE, DI, CL
100
400
400
100
Hysteresis
V
0.1 V
DD
HIS
Output high-level voltage
V
1
OH
PD: I = –1 mA
V – 1.0
DD
V
O
Continued on next page.
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4
LC72121, LC72121M, LC72121V
Continued from preceding page.
Ratings
typ
Parameter
Symbol
Conditions
Unit
min
max
1.0
V
OL1
OL2
PD: IO = 1 mA
V
BO1 to BO4, IO1, IO2: IO = 1 mA
BO1 to BO4, IO1, IO2: IO = 8 mA
DO: IO = 1 mA
0.2
1.6
0.2
1.0
0.5
5.0
5.0
8
V
V
Output low-level voltage
V
V
V
OL3
OL4
DO: IO = 5 mA
V
V
AOUT: IO = 1 mA, AIN = 1.3 V
CE, DI, CL: VI = 6.5 V
IO1, IO2: VI = 13 V
XIN: VI = VDD
V
IIH1
μA
μA
μA
μA
μA
nA
μA
μA
μA
μA
μA
nA
μA
μA
nA
nA
pF
IIH2
IIH3
IIH4
IIH5
IIH6
1.3
Input high-level current
FMIN, AMIN: VI = VDD
IFIN: VI = VDD
2.5
5.0
15
30
AIN: VI = 6.5 V
200
5.0
5.0
8
IIL1
IIL2
IIL3
IIL4
IIL5
IIL6
CE, DI, CL: VI = 0 V
IO1, IO2: VI = 0 V
XIN: VI = 0 V
1.3
2.5
5.0
Input low-level current
FMIN, AMIN: VI = 0 V
IFIN: VI = 0 V
15
30
AIN: VI = 0 V
200
5.0
5.0
200
200
IOFF
1
BO1 to BO4, IO1, IO2, AOUT: VO = 13 V
DO: VO = 6.5 V
Output off leakage current
IOFF2
High-level 3-state off leakage current
Low-level 3-state off leakage current
Input capacitance
IOFFH
IOFFL
CIN
PD: VO = VDD
0.01
0.01
6
PD: VO = 0 V
FMIN
VDD: Xtal = 7.2 MHz, fIN2 = 130 MHz,
IDD1
IDD2
IDD3
2.5
0.3
6
mA
mA
V
IN2 = 20 mVrms
V
DD: PLL block stopped (PLL inhibit mode)
Supply current
Crystal oscillator operating
(crystal frequency: 7.2 MHz)
VDD: PLL block stopped, crystal oscillator
stopped
10
μA
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product performance may not be
indicated by the Electrical Characteristics if operated under different conditions.
Pin Descriptions
Pin No.
Pin
Type
Function
Equivalent circuit
LC72121M
LC72121V
name
LC72121
XIN
1
1
Xtal
• Crystal oscillator element connections (4.5 or 7.2 MHz)
XOUT
22
24
• FMIN is selected when DVS in the serial data is set to 1.
• Input frequency: 10 to 160 MHz
Local
oscillator
signal input
• The signal is passed through an internal divide-by-two prescaler and
then input to the swallow counter.
FMIN
16
17
• The divisor can be set to a value in the range 272 to 65535. Since
the internal divide-by-two prescaler is used, the actual divisor will be
twice the set value.
• AMIN is selected when DVS in the serial data is set to 0.
• When SNS in the serial data is set to 1:
• Input frequency: 2 to 40 MHz
• The signal is input to the swallow counter directly.
Local
oscillator
signal input
• The divisor can be set to a value in the range 272 to 65535. The
set value becomes the actual divisor.
15
AMIN
16
• When SNS in the serial data is set to 0:
• Input frequency: 0.5 to 10 MHz
• The signal is input to a 12-bit programmable divider directly.
• The divisor can be set to a value in the range 4 to 4095. The set
value becomes the actual divisor.
Continued on next page.
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5
LC72121, 72121M, 72121V
Continued from preceding page.
Pin No.
Pin
Type
Function
Equivalent circuit
LC72121M
name
LC72121
LC72121V
• This pin must be set high to enable serial data input (DI) or serial
data output (DO).
CE
DI
3
3
Chip enable
4
5
4
5
Input data
Clock
• Input for serial data transferred from the controller
• Clock used for data synchronization for serial data input (DI) and
serial data output (DO).
CL
• Output for serial data transmitted to the controller. The content of the
data transmitted is determined by DOC0 through DOC2.
DO
6
6
Output data
• LC72121 power supply (VDD 2.7 to 3.6 V)
• The power on reset circuit operates when power is first applied.
VDD
17
18
Power supply
——
VSSX
VSSa
2
2
Ground
Ground
• Ground for the crystal oscillator circuit
——
——
21
22
• Ground for the low-pass filter MOS transistor
• Ground for the LC72121 digital systems other than those that use
VSSd
14
15
Ground
——
VSSa or VSSX
.
• Shared function I/O ports
• The pin function is determined by IOC1 and IOC2 in the serial data.
When the data value 0: Input port
When the data value 1: Output port
• When specified to function as an input port:
The input pin state is reported to the controller through the DO pin.
When the input state is low: The data will be 0:
When the input state is high: The data will be 1:
• When specified to function as an output port:
The output state is determined by IO1 and IO2 in the serial data.
When the data value is 0: The output state will be the open circuit
state.
IO1
IO2
11
13
11
14
I/O port
When the data value is 1: The output state will be a low level.
• These pins are set to input mode after a power on reset.
• Output-only ports
• The output state is determined by BO1 through BO4 in the serial
data.
BO1
BO2
BO3
BO4
7
8
7
8
When the data value is 0: The output state will be the open circuit
state.
When the data value is 1: The output state will be a low level.
• A time base signal (8 Hz) is output from BO1 when TBC in the serial
data is set to 1.
Output port
9
9
10
10
• PLL charge pump output
A high level is output when the frequency of the local oscillator signal
divided by N is higher than the reference frequency, and a low level
is output when that frequency is lower. This pin goes to the high-
impedance state when the frequencies match.
Charge pump
output
PD
18
19
Low-pass filter
amplifier
transistor
AIN
19
20
20
21
• Connections for the MOS transistor used for the PLL active low-pass
filter.
AOUT
• The input frequency range is 0.4 to 15 MHz
• The signal is passed directly to the IF counter.
• The result is output, MSB first, through the DO pin.
• Four measurement periods are supported: 4, 8, 32, and 64 ms.
IFIN
NC
12
—
13
IF counter
12
23
——
NC pin
• No connection
Page 6
LC72121, 72121M, 72121V
Procedures for Input and Output of Serial Data
This product uses the CCB (Computer Control Bus), which is original audio product serial bus format, for data input and
output. This product adopts an 8-bit address CCB format.
Address
I/O mode
IN1 (82)
Function
B0
0
B1
0
B2
0
B3
1
A0
0
A1
1
A2
0
A3
0
• Control data input (serial data input) mode
• 24 bits of data are input.
• See the “DI Control Data (serial data input)” section for details on the
content of the input data.
1
2
3
• Control data input (serial data input) mode
• 24 bits of data are input.
• See the “DI Control Data (serial data input)” section for details on the
content of the input data.
IN2 (92)
1
0
0
1
0
0
1
1
0
0
1
1
0
0
0
0
• Data output (serial data output) mode
• The number of bits output is equal to the number of clock cycles.
• See the “DO output Data (serial data output)” section for details on the
content of the output data.
OUT (A2)
I/O mode determined
Normally high
Normally low
Page 7
LC72121, 72121M, 72121V
Structure of the DI Control Data (serial data input)
• IN1 mode
• IN2 mode
Page 8
LC72121, 72121M, 72121V
DI Control Data
No.
Control block/data
Function
Related data
• Specifies the divisor for the programmable divider.
This is a binary value in which P15 is the MSB. The LSB changes depending on DVS and SNS.
(* : don’t care)
DVS
SNS
LSB
P0
Set divisor (N)
272 to 65535
272 to 65535
4 to 4095
Actual divisor
Twice the set value
The set value
1
0
0
*
1
0
P0
P4
The set value
Programmable
divider data
* LSB: When P4 is the LSB, P0 to P3 are ignored.
P0 to P15
DVS, SNS
1
• These pins select the signal input to the programmable divider (FMIN or AMIN) and switch the input
frequency range.
(* : don’t care)
DVS
SNS
Input pin Frequency range accepted by the input pin
1
0
0
*
1
0
FMIN
AMIN
AMIN
10 to 160 MHz
2 to 40 MHz
0.5 to 10 MHz
* See the “Structure of the Programmable Divider” section for details.
• Reference frequency selection
R3 R2 R1 R0
Reference frequency
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
100
50
kHz
25
25
12.5
6.25
3.125
3.125
10
Reference divider
data
9
5
2
R0 to R3
XS
1
3
15
PLL INHIBIT + Xtal OSC STOP
PLL INHIBIT
* PLL INHIBIT mode
In this mode, the programmable divider and the IF counter block are stopped, the FMIN, AMIN, and IFIN
pins are pulled down to ground, and the charge pump output goes to the high-impedance state.
• Crystal oscillator element selection data
XS = 0: 4.5 MHz
XS = 1: 7.2 MHz
Note that 7.2 MHz is selected after a power on reset.
• IF counter measurement start command data
CTE = 1: Starts the counter
CTE = 0: Resets the counter
• Determines the IF counter measurement time.
IF counter control
data
GT1
GT0
Measurement time
Wait time
3 to 4 ms
3 to 4
3
IFS
CTE
0
0
1
1
0
1
0
1
4 ms
8
GT0, GT1
32
7 to 8
64
7 to 8
* See the “Structure of the IF Counter” section for details.
Continued on next page.
Page 9
LC72121, 72121M, 72121V
Continued from preceding page.
No.
4
Control block/data
Function
Related data
• Specifies input or output for the shared function I/O pins (IO1 and IO2).
I/O port setup data
IOC1,IOC2
Data = 0: Input port
Data = 1: Output port
• Determines the output state of the BO1 through BO4, IO1, and IO2 output ports.
Data = 0: Open
Data = 1: Low level
Output port data
BO1 to BO4
IO1,IO2
IOC1
IOC2
5
• The data is reset to 0, setting the pins to the open state, after a power on reset.
• Determines the DO pin output.
DOC2
DOC1
DOC0
DO pin state
Open
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Low when the PLL is unlocked
end-UC *1
Open
Open
The IO1 pin state *2
The IO2 pin state *2
Open
UL0, UL1
CTE
The open state is selected after a power on reset.
*1. end-UC: IF counter measurement end check
DO pin control data
DOC0
6
DOC1
IOC1
IOC2
DOC2
(1)When end-UC is selected and an IF count is started (by switching CTE from 0 to 1), the DO pin
automatically goes to the open state.
(2)When the IF counter measurement period completes, the DO pin goes to the low level, allowing
applications to test for the completion of the count period.
(3)The DO pin is set to the open state by performing a serial data input or output operation (when the CE
pin is set high).
*2. The DO pin will go to the open state if the corresponding IO pin is set up to be an output port.
Note: During the data input period (the period that CE is high in IN1 or IN2 mode), the DO pin goes to the
open state regardless of the DO pin control data (DOC0 to DOC2). During the data output period (the
period that CE is high in OUT mode) the DO pin state reflects the internal DO serial data in
synchronization with the CL clock, regardless of the DO pin control data (DOC0 to DOC2).
• Selects the width of the phase error (øE) detected for PLL lock state discrimination. The state is taken to
be unlocked if a phase error in excess of the detection width occurs.
UL1
0
UL0
0
øE detection width
Stopped
0
Detection output
Open
DOC0
DOC1
DOC2
Unlocked state
detection data
7
0
1
øE is output directly
øE is extended by 1 to 2 ms
øE is extended by 1 to 2 ms
UL0, UL1
1
0
±0.55 µs
±1.11 µs
1
1
* When the PLL is unlocked, the DO pin goes low and UL in the serial data output is set to 0.
• Controls the phase comparator dead zone
DZ1
0
DZ
0
Dead zone mode
DZA
DZB
DZC
DZD
Phase comparator
control data
8
0
1
DZ0, DZ1
1
0
1
1
Dead zone width: DZA < DZB < DZC < DZD
Continued on next page.
Page 10
LC72121, 72121M, 72121V
Continued from preceding page.
No.
9
Control block/data
Function
Related data
BO1
Clock time base
TBC
• Setting the TBC bit to 1 causes an 8-Hz clock time base signal with a 40% duty to be output from the
BO1 pin. (The BO1 data will be ignored.)
• Forcibly controls the charge pump output.
DLC
Charge pump output
Normal operation
Forced to low
0
1
Charge pump
control data
10
11
DLC
* If the circuit deadlocks due to the VCO control voltage (Vtune) being 0 and the VCO being stopped,
applications can get out of the deadlocked state by setting the charge pump output to low and setting
Vtune to VCC. (Deadlock clear circuit)
IF counter control
data
• This data is normally set to 1. Setting this data to 0 sets the circuit to reduced input sensitivity mode, in
which the sensitivity is reduced by about 10 to 30 mV rms.
* See the “IF Counter Operation” section for details.
IFS
• Test data
TEST0
Test data
12
13
TEST1
TEST2
All these bits must be set to 0.
TEST0 to 2
All these bits are set to 0 after a power on reset.
DNC
• This bit must be set to 0.
Structure of the DO Output Data (serial data output)
• OUT mode
DO Output Data
No. Control block/data
Function
Related data
• Data latched from the I/O port IO1 or IO2 pin states.
• These bits reflect the pin states regardless of the I/O port mode (input or output).
The data is latched at the point the circuit enters data output mode (OUT mode).
I/O port data
12, I1
IOC1
IOC2
1
I1 ← The IO1 pin state
I2 ← The IO2 pin state
H : 1
L : 0
PLL unlocked state
data
• Indicates the state of the unlocked state detection circuit.
UL ← 0: When the PLL is unlocked.
UL0
UL1
2
3
UL ← 1: When the PLL is locked or in the detection disabled mode.
UL
IF counter binary
data
• Indicates the value of the IF counter (20-bit binary counter).
C19 ← MSB of the binary counter
CTE
GT0
GT1
C0 ← LSB of the binary counter
C19 to C0
Page 11
LC72121, 72121M, 72121V
Serial Data Input (IN1/IN2) t , t , t , t , t ≥ 0.75 µs t < 0.75 µs
SU HD EL ES EH
LC
• CL: Normally high
• CL: Normally low
Serial Data Output (Out) t , t , t , t , t ≥ 0.75 µs t , t < 0.35 µs
SU HD EL ES EH
DC DH
• CL: Normally high
• CL: Normally low
Note:
The data conversion times (tDC and tDH) depend on the value of the pull-up resistor and the printed circuit board capacitance since the DO pin is an
n-channel open-drain circuit.
Page 12
LC72121, 72121M, 72121V
Serial Data Timing
When CL is Stopped at the Low Level
When CL is Stopped at the High Level
Ratings
typ
Parameter
Symbol
Conditions
Unit
min
0.75
max
Data setup time
Data hold time
tSU
tHD
tCL
tCH
tEL
tES
tEH
tLC
tDC
tDH
DI, CL
DI, CL
CL
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
0.75
0.75
0.75
0.75
0.75
0.75
Clock low level time
Clock high level time
CE wait time
CL
CE, CL
CE, CL
CE, CL
CE setup time
CE hold time
Data latch change time
0.75
DO, CL These values differ depending on the value of the pull-up
DO, CE resistor used and the printed circuit board capacitance.
0.35
0.35
Data output time
Page 13
LC72121, 72121M, 72121V
Structure of the Programmable Divider
DVS
SNS
Input pin
FMIN
Set divisor
272 to 65535
272 to 65535
4 to 4095
Actual divisor
Twice the set value
The set value
Input frequency range
10 to 160 MHz
2 to 40 MHz
A
B
C
1
0
0
*
1
0
AMIN
AMIN
The set value
0.5 to 10 MHz
*: Don’t care
Sample Programmable Divider Divisor Calculations
• For FM with a step size of 50 kHz (DVS = 1, SNS = *: FMIN selected)
FM RF = 90.0 MHz (IF +10.7 MHz)
FM VCO = 100.7 MHz
PLL fref = 25 kHz (R0 = 0, R1 = 1, R2 = 0, R3 = 0)
100.7 MHz (FM VCO) ÷ 25 kHz (fref) ÷ 2 (for the FMIN 1/2 prescaler) 2014 → 07DE (hexadecimal)
• For SW with a step size of 5 kHz (DVS = 0, SNS = 1: AMIN high-speed operation selected)
SW RF = 21.75 MHz (IF +450 kHz)
SW VCO = 22.20 MHz
PLL fref = 5 kHz (R0 = 0, R1 = 1, R2 = 0, R3 = 1)
22.2 MHz (SW VCO) ÷ 5 kHz (fref) = 4440 → 1158 (hexadecimal)
• For MW with a step size of 9 kHz (DVS = 0, SNS = 0: AMIN low-speed operation selected)
MW RF = 1008 kHz (IF +450 kHz)
WM VCO = 1458 kHz
PLL fref =9 kHz (R0 = 1, R1 = 0, R2 = 0, R3 = 1)
1458 (MW VCO) ÷ 9 kHz (fref) = 162 → 0A2 (hexadecimal)
Page 14
LC72121, 72121M, 72121V
Structure of the IF Counter
The LC72121 IF counter is a 20-bit binary counter, and takes the IF signal from the IFIN pin as its input. The result of
the count can be read out serially, MSB first, from the DO pin.
Measurement time
GT1
GT0
Measurement time (GT)
Wait time (tWU
3 to 4 ms
)
0
0
1
1
0
1
0
1
4 ms
8
3 to 4 ms
32
7 to 8 ms
64
7 to 8 ms
The IF frequency (Fc) is measured by determining how many pulses were input to the IF counter in the stipulated
measurement time, GT.
C
GT
Fc =—— (C = Fc x GT)
C: Counted value (the number of pulses)
IF Counter Frequency Measurement Examples
• When the measurement time (GT) is 32 ms and the counted value (C) is 53980 (hexadecimal) or 342,400 (decimal).
IF frequency (F ) = 342400 ÷ 32 ms = 10.7 MHz
C
• When the measurement time (GT) is 8 ms and the counted value (C) is E10 (hexadecimal) or 3600 (decimal).
IF frequency (F ) = 3600 ÷ 8 ms = 450 kHz
C
Page 15
LC72121, 72121M, 72121V
IF Counter Operation
Applications must first, before starting an IF count operation reset the IF counter by setting CTE in the serial data to 0.
The IF counter operation is started setting CTE in the serial data from 0 to 1. Although the serial data is latched by
dropping the CE pin from high to low, the IF signal input to the IFIN pin must be provided within the wait time from the
point CE goes low. Next, the readout of the IF counter after measurement is complete must be performed while CTE is
still 1, since the counter will be reset if CTE is set to 0.
Note: If IF counting is used, applications must determine whether or not the IF IC SD (station detect) signal is present in
the microcontroller software, and perform the IF count only if that signal is asserted. This is because auto-search
techniques that use IF counting only are subject to incorrect stopping at points where there is no station due to IF
buffer leakage.
Note that the LC72121 input sensitivity can be controlled with the IFS bit in the serial data.
Reduced sensitivity mode (IFS = 0) must be selected when this IC is used in conjunction with an IF IC that does
not provide an SD output and auto-search is implemented using only IF counting.
IFIN Minimum Sensitivity Standard
Input frequency : f [MHz]
IFS data
0.4 ≤ f < 0.5
0.5 ≤ f < 8
40 mVrms
70 mVrms
8 ≤ f ≤ 15
1(Normal mode)
40 mVrms (0.1 to 3 mVrms)
70 mVrms (5 to 10 mVrms)
40 mVrms (1 to 15 mVrms)
70 Vrms (30 to 40 mVrms)
0 (Degraded sensitivity mode)
Note: Values in parentheses are actual performance values that are provided for reference purposes.
Page 16
LC72121, 72121M, 72121V
Unlocked State Detection Timing
• Unlocked state detection timing
Unlocked state detection is performed during the reference frequency (fref) period (interval). This means that a period
at least as long as the period of the reference frequency is required to recognize the locked/unlocked state. However,
applications must wait at least twice the period of the reference frequency immediately after changing the divisor (N)
before checking the locked/unlocked state.
Figure 1 Unlocked State Detection Timing
For example, if fref is 1 kHz (a period of 1 ms) applications must wait at least 2 ms after the divisor N is changed
before performing a locked/unlocked check.
Figure 2 Circuit Structure
Page 17
LC72121, 72121M, 72121V
Figure 3 Combining with Software
• Outputting the unlocked state data in the serial data
At the point of data output 1 in figure 3, the unlocked state data will indicate the unlocked state, since the VCO
frequency is not stable (locked) yet. In cases such as this, the application should wait at least one whole period and then
check again whether or not the frequency has stabilized with the data output 2 operation in the figure. Applications can
implement even more reliable recognition of the locked state by performing several more checks of the state and
requiring that the locked state be detected sequentially.
<Flowchart for Lock Detection>
Divisor N changed (data input)
Wait at least 2 reference frequency periods.
Data output (1)
Valid output data is acquired by using an interval of at
least one reference frequency period.
Data output (2)
*: Even more reliable recognition of the locked state
can be achieved by performing several checks of the
state and requiring that the locked state be detected
sequentially.
Locked state check
NO
*
YES
A10180
• Directly outputting the unlocked state to the DO pin
Since the unlocked state (high level when locked, low when unlocked) is output from the DO pin, applications can
check for the locked state by waiting at least two reference frequency periods after changing the divisor N. However, in
this case also, even more reliable recognition of the locked state can be achieved by performing several checks of the
state and requiring that the locked state be detected sequentially.
Page 18
LC72121, 72121M, 72121V
Clock Time Base Usage Notes
When using the clock time base output function, the output pin (BO1) pull-up resistor must have a value of over 100 kΩ.
The use of a Schmitt input in the microcontroller that accepts this signal is recommended to reduce chattering. This is to
prevent degradation of the VCO C/N characteristics when combining with a loop filter that uses the internal transistor
provided to form a low-pass filter. Although the ground for the clock time base output pin (V ) and the ground for the
SSd
transistor (V ) are isolated internally on the chip, applications must take care to avoid ground loops and minimize
SSa
current fluctuations in the time base pin to prevent degradation of the low-pass filter characteristics.
Pin States after a Power on Reset
Page 19
LC72121, 72121M, 72121V
Sample Application Circuit
(Using the DIP22S package)
Since this is a high-impedance circuit,
it is susceptible to noise. Therefore,
lines in the printed circuit board
pattern should be made as short as
possible and it should be surrounded
by the ground pattern.
Page 20
LC72121, 72121M, 72121V
Other Items
• Notes on the phase comparator dead zone
DZ1
0
DZ0
0
Dead zone mode
Charge pump
ON/ON
Dead zone
– –0s
–0s
DZA
DZB
DZC
DZD
0
1
ON/ON
1
0
OFF/OFF
OFF/OFF
+0s
1
1
+ +0s
When the charge pump is used with one of the ON/ON modes, correction pulses are generated from the charge pump
even if the PLL is locked. As a result, it is easy for the loop to become unstable, and special care is required in
application design. The following problems can occur if an ON/ON mode is used.
— Sidebands may be created by reference frequency leakage.
— Sidebands may be created by low-frequency leakage due to the correction pulse envelope.
Although the loop is more stable when a dead zone is present (i.e. when an OFF/OFF mode is used), a dead zone
makes it more difficult to achieve excellent C/N characteristics. On the other hand, while it is easy to achieve good C/N
characteristics when there is no dead zone, achieving good loop stability is difficult. Accordingly, the DZA and DZB
settings, in which there is no dead zone, can be effective in situations where a signal-to-noise ratio of 90 to 100 dB or
higher is required in FM reception, or where it is desirable to increase the pilot margin in AM stereo reception.
However, if such a high signal-to-noise ratio is not required for FM reception, if an adequate pilot margin can be
acquired in AM stereo reception, or if AM stereo is not required, then either DZC or DZD, in which there is a dead
zone, should be chosen.
Dead Zone
As shown in figure 1, the phase comparator compares a reference frequency (fr) with fp. As shown in figure 2, the phase
comparator's characteristics consist of an output voltage (V) that is proportional to the phase difference ø. However, due
to internal circuit delay and other factors, an actual circuit has a region (the dead zone, B) where the circuit cannot
actually compare the phases. To implement a receiver with a high S/N ratio, it is desirable that this region be as small as
possible. However, it is often desirable to have the dead zone be slightly wider in popularly-priced models. This is
because in certain cases, such as when there is a strong RF input, popularly-priced models can suffer from mixer to VCO
RF leakage that modulates the VCO. When the dead zone is small, the circuit outputs signals to correct this modulation
and this output further modulates the VCO. This further modulation may then generate beats and the RF signal.
Figure 1
Figure 2
• Notes on the FMIN, AMIN, and IFIN pins
Coupling capacitors should be placed as close to their pin as possible. A capacitance of about 100 pF is desirable for
these capacitors. In particular, if the IFIN pin coupling capacitor is not held under 1000 pF, the time to reach the bias
level may become excessive and incorrect counts may result due to the relationship with the wait time.
• Notes on IF counting → Use the SD signal in conjunction with IF counting
When counting the IF frequency, the microcontroller must determine the presence or absence of the IF IC SD (station
detect) signal and turn on the IF counter buffer output and execute the IF count only if there is an SD signal. Auto-
search techniques that only use the IF counter are subject to incorrect stopping at points where there is no station due to
IF buffer leakage.
Page 21
LC72121, 72121M, 72121V
• DO pin usage
The DO pin can be used for IF counter count completion checking and as an unlock detection output in addition to its
use in data output mode. It is also possible to have the DO pin reflect the state of an input pin to input that state to the
microcontroller.
• Power supply pins
Capacitors must be inserted between the power supply V and V pins for noise exclusion. These capacitors must be
DD
SS
placed as close as possible to the V and V pins.
DD
SS
• VCO setup
Applications must be designed so that the VCO (local oscillator) does not stop, even if the control voltage (Vtune) goes
to 0 V. If it is possible for the oscillator to stop, the application must use the control data (DLC) to temporarily force
Vtune to V to prevent deadlock from occurring. (Deadlock clear circuit)
CC
• Front end connection example
Since this product (and the LC72131 as well) is designed with the relatively high resistance of 200 kΩ for the pull-
down (on) resistors built in to the FMIN and AMIN pins, a common AM/FM local oscillator buffer can be used as
shown in the following circuit.
• PD pin
Note that the charge pump output voltage is reduced when this IC, which is a 3-V system, is used to replace the
LC72131, which is a 5-V system. This means that since the loop gain is reduced, the loop filter constants, the lock time
(SD wait time), and other related parameters must be reevaluated in the end product design.
Page 22
LC72121, LC72121M, LC72121V
Package Dimensions
unit : mm
[LC72121]
PDIP22 / DIP22S (300 mil)
CASE 646AV
ISSUE A
GENERIC
MARKING DIAGRAM*
XXXXXXXXXX
YMDDD
XXXXX = Specific Device Code
Y = Year
M = Month
DDD = Additional Traceability Data
*This information is generic.
www.onsemi.com
23
LC72121, LC72121M, LC72121V
Package Dimensions
unit : mm
[LC72121M]
SOIC24 W / MFP24S (300 mil)
CASE 751CG
ISSUE O
to
www.onsemi.com
24
LC72121, LC72121M, LC72121V
Package Dimensions
unit : mm
[LC72121V]
SSOP24 (275mil)
CASE 565AQ
ISSUE A
SOLDERING FOOTPRINT*
(Unit: mm)
GENERIC
MARKING DIAGRAM*
XXXXXXXXXX
YMDDD
XXXXX = Specific Device Code
Y = Year
M = Month
0.65
0.32
DDD = Additional Traceability Data
NOTE: The measurements are not to guarantee but for reference only.
*This information is generic.
*For additional information on our Pb-Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
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25
LC72121, LC72121M, LC72121V
ORDERING INFORMATION
Device
Package
Shipping (Qty / Packing)
DIP22S(300mil)
(Pb-Free)
LC72121-D-E
22 / Fan-Fold
2000 / Tape and Reel
60 / Fan-Fold
MFP24S(300mil)
(Pb-Free)
LC72121M-TLM-E
LC72121V-D-MPB-E
LC72121V-D-TML-E
LC72121V-TLM-E
SSOP24(275mil)
(Pb-Free)
SSOP24(275mil)
(Pb-Free)
1000 / Tape and Reel
1000 / Tape and Reel
SSOP24(275mil)
(Pb-Free)
† For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel
Packaging Specifications Brochure, BRD8011/D. http://www.onsemi.com/pub_link/Collateral/BRD8011-D.PDF
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Semiconductor reserves the right to make changes without further notice to any products herein. ON Semiconductor makes no warranty, representation or
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