Datasheet LC72137M Datasheet (SANYO)

CMOS IC

Ordering number : EN5743

70398RM(OT) No. 5743-1/23

SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters

TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN

PLL Frequency Synthesizer

for Electronic Tuning

LC72137, 72137M

Overview

The LC72137 and LC72137M are PLL frequency
synthesizers for use in radio/cassette players. They allow
high-performance AM/FM tuners to be implemented
easily.

Features

• High-speed programmable frequency divider

— FMIN: 10 to 160 MHz.....Pulse swallower

(divide-by-two prescaler built in)

— AMIN: 2 to 40 MHz.........Pulse swallower

0.5 to 10 MHz......Direct division

• IF counter

IFIN: 0.4 to 12 MHz................For use as an AM/FM IF

counter

• Reference frequency
— Selectable from one of eight frequencies (crystal

oscillator: 75 kHz)
1, 3, 5, 3.125, 6.25, 12.5, 15, and 25 kHz

• Phase comparator
— Supports dead zone control
— Built-in unlock detection circuit
— Built-in deadlock clear circuit

• Built-in MOS transistor for forming an active low-pass

filter

• I/O ports
— Dedicated output ports: 4
— I/O ports: 2
— Supports clock time base output

• Serial Data I/O
— Supports CCB format communication with the

system controller.

• Operating ranges
— Supply voltage: 2.5 to 3.6 V
— Operating temperature: –20 to +70°C

• Packages

—DIP22S/MFP20

Package Dimensions

unit: mm

3059-DIP22S

SANYO: DIP22S

[LC72137]

• CCB is a trademark of SANYO ELECTRIC CO., LTD.

• CCB is SANYO’s original bus format and all the bus
addresses are controlled by SANYO.

unit: mm

3036B-MFP20

SANYO: MFP20

[LC72137M]

No. 5743-2/23

LC72137, 72137M

Specifications

Absolute Maximum Ratings at Ta = 25°C, VSS= 0 V

Parameter Symbol Conditions Ratings Unit

Maximum supply voltage V

DD

max V

DD

–0.3 to +7.0 V

V

IN

1 max CE, CL, DI, AIN –0.3 to +7.0 V

Maximum input voltage V

IN

2 max XIN, FMIN, AMIN, IFIN –0.3 to VDD+ 0.3 V

V

IN

3 max IO1, IO2 –0.3 to +15 V

V

O

1 max DO –0.3 to +7.0 V

Maximum output voltage V

O

2 max XOUT, PD –0.3 to VDD+ 0.3 V

V

O

3 max BO1 to BO5, BOF, IO1, IO2, AOUT –0.3 to +15 V

Maximum output current I

O

max BO1 to BO4, IO1, IO2, DO, AOUT 0 to 6.0 mA

Allowable power dissipation Pd max

Ta ≤ 70°C: LC72136N (DIP22S) 350 mW

Ta ≤ 70°C: LC72136NM (MFP20) 180 mW
Operating temperature Topr –20 to +70 °C
Storage temperature Tstg –40 to +125 °C

Ratings

Parameter Symbol Conditions

min typ max

Unit

Supply voltage V

DD

V

DD

2.5 3.6 V

Input high-level voltage

V

IH

1 CE, CL, DI 0.7 V

DD

6.5 V

V

IH

2 IO1, IO2 0.7 V

DD

13 V

Input low-level voltage V

IL

CE, CL, DI, IO1, IO2 0 0.3 V

DD

V

Output voltage

V

O

1 DO 0 6.5 V

V

O

2 BO1 to BO4, IO1, IO2, AOUT 0 13 V

f

IN

1 XIN: VIN1 75 kHz

f

IN

2 FMIN: VIN2 10 160 MHz

Input frequency f

IN

3 AMIN: VIN3, SNS = 1 2 40 MHz

f

IN

4 AMIN: VIN4, SNS = 0 0.5 10 MHz

f

IN

5 IFIN: VIN5 0.4 12 MHz

V

IN

1 XIN: fIN1 200 800 mVrms

V

IN

2-1 FMIN: f = 10 to 130 MHz 20 800 mVrms

V

IN

2-2 FMIN: f = 130 to 160 MHz 40 800 mVrms

Input amplitude V

IN

3 AMIN: fIN3, SNS = 1 40 800 mVrms

V

IN

4 AMIN: fIN4, SNS = 0 40 800 mVrms

V

IN

5-1 IFIN: fIN5, IFS = 1 40 800 mVrms

V

IN

5-2 IFIN: fIN6, IFS = 0 70 800 mVrms

Guaranteed crystal

Xtal XIN, XOUT * 75 kHz

oscillator frequency

Allowable Operating Ranges at Ta = –20 to +70°C, VSS= 0 V

* Note : Recommended crystal oscillator CI value : CI ≤ 35 kΩ

No. 5743-3/23

LC72137, 72137M

Electrical Characteristics within the allowable operating ranges

Ratings

Parameter Symbol Conditions

min typ max

Unit

Rf1 XIN 8.0 MΩ

Internal feedback resistors

Rf2 FMIN 500 kΩ
Rf3 AMIN 500 kΩ
Rf4 IFIN 250 kΩ

Internal pull-down resistors

Rpd1 FMIN 200 kΩ

Rpd2 AMIN 200 kΩ
Internal output resistor Rd XOUT 250 kΩ
Hysteresis V

HIS

CE, CL, DI, IO1, IO2 0.1 V

DD

V

Output high-level voltage V

OH

1 PD: IO= –1 mA VDD– 1.0 V

V

OL

1 PD: IO= 1 mA 1.0 V

V

OL

2

BO1 to BO4, IO1, IO2; I

O

= 1 mA 0.25 V

Output low-level voltage BO1 to BO4, IO1, IO2; I

O

= 5 mA 1.25 V

V

OL

3 DO: IO= 1 mA 0.25 V

V

OL

4 AOUT, AIN= 1.3 V 0.5

I

IH

1 CE, CL, DI: VI= 6.5 V 5.0 µA

I

IH

2 IO1, IO2: VI= 13 V 5.0 µA

Input high-level voltage

I

IH

3 XIN: VI= V

DD

0.16 0.9 µA

I

IH

4 FMIN, AMIN: VI= V

DD

2.5 15 µA

I

IH

5 IFIN: VI= V

DD

5.0 30 µA

I

IH

6 AIN: VI= 6.5 V 200 nA

I

IL

1 CE, CL, DI: VI= 0 V 5.0 µA

I

IL

2 IO1, IO2: VI= 0 V 5.0 µA

Input low-level current

I

IL

3 XIN: VI= 0 V 0.16 0.9 µA

I

IL

4 FMIN, AMIN: VI= 0 V 2.5 15 µA

I

IL

5 IFIN: VI= 0 V 5.0 30 µA

I

IL

6 AIN: VI= 0 V 200 nA

Output off leakage current

I

OFF

1 BO1 to BO4, AOUT, IO1, IO2: VO= 13 V 5.0 µA

I

OFF

2 DO: VO= 6.5 V 5.0 µA

High-level three-state off

I

OFFH

PD: VO= V

DD

0.01 200 nA

leakage current
Low-level three-state off

I

OFFL

PD: VO= 0 V 0.01 200 nA

leakage current
Input capacitance C

IN

FMIN 6 pF

I

DD

1 VDD: Xtal = 75 kHz, fIN2 = 130 MHz, VIN2 = 20 mVrms 2.5 6 mA

Current drain I

DD

2

V

DD

: PLL block stopped (PLL inhibit),

20 mA

Xtal oscillator operating (Xtal = 75 kHz)

I

DD

3 VDD: PLL block stopped, Xtal oscillator stopped 10 µA

No. 5743-4/23

LC72137, 72137M

Pin Assignments

No. 5743-5/23

LC72137, 72137M

Block Diagram

No. 5743-6/23

LC72137, 72137M

Pin Descriptions

Pin No.

Symbol (MFP pin numbers Type Functions Circuit configuration

are in parentheses.)

20 (19)
21 (21)

13 (12)

12 (11)

2 (1)

4 (3)

3 (2)

5 (4)

15 (14)

16 (15)

XIN

XOUT

FMIN

AMIN

CE

CL

DI

DO

V

DD

V

SS

Xtal

Local oscillator
signal input

Local oscillator
signal input

Chip enable

Clock

Input data

Output data

Power supply

Ground

• Crystal oscillator connections (75 kHz)

• FMIN is selected when the serial data input DVS bit is
set to 1.

• The input frequency range is from 10 to 160 MHz.

• The input signal passes through the internal divide-by­two prescaler and is input to the swallow counter.

• The divisor can be in the range 272 to 65535. However,
since the signal has passed through the divide-by-two
prescaler, the actual divisor is twice the set value.

• AMIN is selected when the serial data input DVS bit is
set to 0.

• When the serial data input SNS bit is set to 1:
— The input frequency range is 2 to 40 MHz.
— The signal is directly input to the swallow counter.
— The divisor can be in the range 272 to 65535, and

the divisor used will be the value set.

• When the serial data input SNS bit is set to 0:
— The input frequency range is 0.5 to 10 MHz.
— The signal is directly input to a 12-bit programmable

divider.

— The divisor can be in the range 4 to 4095, and the

divisor used will be the value set.

• Set this pin high when inputting (DI) or outputting (DO)
serial data.

• Used as the synchronization clock when inputting (DI) or
outputting (DO) serial data.

• Inputs serial data transferred from the controller to the
LC72137.

• Outputs serial data transferred from the LC72137 to the
controller. The data output is determined by the DOC0 to
DOC2 bits in the serial data.

• The LC72137 power supply pin. (V

DD

= 2.5 to 3.6 V)

• The power on reset circuit operates when power is first
applied.

• The LC72137N ground

Continued on next page.

No. 5743-7/23

LC72137, 72137M

Continued from preceding page.

Pin No.

Symbol (MFP pin numbers Type Functions Circuit configuration

are in parentheses.)

6 (5)
7 (6)
8 (7)

14 (13)

9 (8)

10 (9)

17 (16)

18 (17)
19 (18)

10 (9)

BO1
BO2
BO3
BO4

IO1
IO2

PD

AIN

AOUT

NC

Output ports

Input or output
ports

Charge pump
output

LPF amplifier
transistor
connections

IF counter

• Dedicated outputs

• The output states are determined by the BO1 to BO5
bits in the serial data.
Data: 0 = open, 1= low

• A time base signal (8 Hz) can be output from the BO1
pin. (When the serial data TBC bit is set to 1.)

• I/O dual-use pins

• The direction (input or output) is determined by bits IOC1
and IOC2 in the serial data.
Data: 0 = input port, 1 = output port

• When specified for use as input ports:
The state of the input pin is transmitted to the controller
over the DO pin.
Input state: low = 0 data value

high = 1 data value

• When specified for use as output ports:
The output states are determined by the IO1 and IO2
bits in the serial data.
Data: 0 = open, 1 = low

• These pins function as input pins following a power on
reset.

• PLL charge pump output
When the frequency generated by dividing the local
oscillator signal frequency by N is higher than the
reference frequency, a high level is output from the PD
pin. Similarly, when that frequency is lower, a low level is
output. The PD pin goes to the high-impedance state
when the frequencies match.

• The n-channel MOS transistor used for the PLL active
low-pass filter.

• Accepts an input in the frequency range 0.4 to 12 MHz.

• The input signal is directly transmitted to the IF counter.

• The result is output starting the MSB of the IF counter
using the DO pin.

• Four measurement periods are supported: 4, 8, 16, and
32 ms.

IFIN

1 (–)

22 (–)

NC Pin

• No connection

No. 5743-8/23

LC72137, 72137M

Serial Data I/O Procedures

The LC72137 inputs and outputs data using the Sanyo CCB (computer control bus) audio IC serial bus format. This IC
adopts an 8-bit address format CCB.

I/O mode

Address

Function

B0 B1 B2 B3 A0 A1 A2 A3

1

2

3

IN1 (82)

IN2 (92)

OUT (A2)

0 0 0 1 0 1 0 0

1 0 0 1 0 1 0 0

0 1 0 1 0 1 0 0

• Control data input mode (serial data input)

• 24 data bits are input.

• See the “DI Control Data (serial data input) Structure”
item for details on the meaning of the input data.

• Control data input mode (serial data input)

• 24 data bits are input.

• See the “DI Control Data (serial data input) Structure”
item for details on the meaning of the input data.

• Data output mode (serial data output)

• The number of bits output is equal to the number of clock
cycles.

• See the “DO Output Data (Serial Data Output) Structure”
item for details on the meaning of the output data.

No. 5743-9/23

LC72137, 72137M

DI Control Data (serial data input) Structure

1. IN1 Mode

2. IN2 Mode

No. 5743-10/23

LC72137, 72137M

DI Control Data Descriptions

No. Control block/data Description Related data

Programmable divider data • Data that sets the programmable divider
P0 to P15 A binary value in which P15 is the MSB. The LSB changes depending on DVS and SNS.

(*: Don’t care.)

Note: P0 to P3 are ignored when P4 is the LSB.

DVS, SNS • Selects the signal input pin (AMIN or FMIN) for the programmable divider, switches the

frequency range. (*: Don’t care.)

Note: See the “Programmable Divider” item for details.

Reference divider data • Reference frequency (fref) selection data
R0 to R3

Note: PLL INHIBIT

The programmable divider and IF counter blocks are stopped, the FMIN, AMIN,
and IFIN pins go to the pulled-down state, and the charge pump output pin goes to
the high-impedance state.

IF counter control data • IF counter measurement start specification
CTE CTE = 1: Counter start

CTE = 0: Counter reset

GT0, GT1 • IF counter measurement time determination

Note: See the “IF Counter Structure” item for details.

I/O port specification data • Data that specifies input or output for the I/O dual-use pins (IO1, IO2)
IOC1, IOC2 Data: 0 = input mode, 1 = output mode

Output port data • BO1 to BO4, IO1, and IO2 output state data
BO1 to BO4, IO1, IO2 Data: 0 = open, 1 = low

• “Data = 0: Open” is selected following a power-on reset.

(1)

(2)

(3)

(4)

(5)

IFS

IOC1
IOC2

DVS SNS LSB Divisor setting (N) Actual divisor

1 * P0 272 to 65535 Twice the value of the setting
0 1 P0 272 to 65535 The value of the setting
0 0 P4 4 to 4095 The value of the setting

DVS SNS Input pin Input frequency range

1 * FMIN 10 to 160 MHz
0 1 AMIN 2 to 40 MHz
0 0 AMIN 0.5 to 10 MHz

GT1 GT0 Measurement time (ms) Wait time (ms)

0 0 4 3 to 4
0 1 8 3 to 4
1 0 16 7 to 8
1 1 32 7 to 8

R3 R2 R1 R0 Reference frequency (kHz)

0 0 0 0 25
0 0 0 1 25
0 0 1 0 25
0 0 1 1 25
0 1 0 0 12.5
0 1 0 1 6.25
0 1 1 0 3.125
0 1 1 1 3.125

1 0 0 0 5
1 0 0 1 5
1 0 1 0 5
1 0 1 1 1

1 1 0 0 3
1 1 0 1 15

1 1 1 0 PLL INHIBIT + Xtal OSC STOP
1 1 1 1 PLL INHIBIT

Continued on next page.

No. 5743-11/23

LC72137, 72137M

Continued from preceding page.

No. Control block/data Description Related data

DO pin control data • Data that determines DO pin output
DOC0, DOC1, DOC2

The open state is selected following a power-on reset.
Note: 1. end-UC: IF counter measurement completion check

➀ When end-UC is set and an IF count is started (CTE = 0 → 1), the DO pin

automatically goes to the open state.

➁ When the IF count measurement completes, the DO pin goes low and

the count completion check operation is enabled.

➂ The DO pin goes to the open state due to serial data I/O (CE: high).

2. Goes to the open state if the IO pin itself is set to be an output port.

Caution: The DO pin always goes to the open state during the data input period (during the

period when CE is high in mode IN1 or IN2), regardless of the values of the DO pin
control data (DOC0 to DOC2). Also, the DO pin outputs the content of the internal
DO serial data in synchronization with the CL pin signal during the data output period
(during the period when CE is high in the OUT mode) regardless of the values of
the DO pin control data (DOC0 to DOC2).

Unlock detection data • Selects the phase error (øE) detection range for PLL lock discrimination.
UL0, UL1 When a phase error greater than the specified range occurs, the LC72136N determines

that the PLL is unlocked. (*: Don’t care.)

Note: When unlocked, the DO pin goes low and the serial data output UL bit is 0.

Phase comparator • Phase comparator dead zone control data
control data
DZ0, DZ1

Dead zone width: DZA < DZB < DZC < DZD

Clock time base • An 8 Hz 40% duty clock time base signal can be output from BO1 by setting TBC to 1.
TBC (The BO1 data will be ignored.)

Charge pump control data • Data that forcibly controls the charge pump output
DLC

Note: The LC72137 provides a technique for escaping from deadlock by setting Vtune to

V

CC

(deadlock clear circuit). This is used when the circuit is deadlocked due to the

VCO oscillator being stopped by the VCO control voltage (Vtune) being 0 V.

(6)

(7)

(8)

(9)

(10)

UL0, UL1,
CTE,
IOC1, IOC2

DOC0,
DOC1,
DOC2

BO1

DOC2 DOC1 DOC0 DO pin state

0 0 0 Open
0 0 1 Low when the unlock state is detected
0 1 0 end-UC

*1

0 1 1 Open
1 0 0 Open

1 0 1 The IO1 pin state

*2

1 1 0 The IO2 pin state

*2

1 1 1 Open

UL1 UL0 øE detection width Detector output

0 0 Stopped Open
0 1 0 øE is output directly
1 * ±6.67 µs øE is extended by 1 to 2 ms

DZ1 DZ0 Dead zone mode

0 0 DZA
0 1 DZB
1 0 DZC
1 1 DZD

DLC Charge pump output

0 Normal operation
1 Forced low

Continued on next page.

No. 5743-12/23

LC72137, 72137M

Continued from preceding page.

DO Output Data (Serial Data Output) Structure

3. OUT mode

DO Output Data

No. Control block/data Description Related data

IF counter control data • This data should be set to 1 in normal operation. Setting this data to 0 switches

(11) IFS the LC72137 to a reduced input sensitivity mode in which the sensitivity is reduced by

10 to 30 mVrms.
LSI test data • IC test data
TEST 0 to TEST2 TEST0

(12)

TEST1 All three bits must be set to 0.

TEST2

All the test data is set to 0 at a power-on reset.

(13) DNC Data is set to 0

No. Control block/data Description Related data

I/O port data • Data latched from the states of the I/O ports, pins IO1 and IO2.
I2, I1 • This data reflects the pin states, regardless of whether they are in input or output mode.

• The data is latched when OUT mode is selected.
I1 ← IO1 pin state High: 1

I2 ← IO2 pin state Low: 0

PLL unlock data • Data latched from the state of the unlock detection circuit
UL UL ← 0: Unlocked

UL ← 1: Locked or in detection stopped mode

IF counter binary data • Data latched from the state of the IF counter, which is a 20-bit binary counter.
C19 to C0 C19 ← Binary counter MSB

C0 ← Binary counter LSB

(1)

(2)

(3)

IOC1,
IOC2

UL0,
UL1

CTE,
GT0,
GT1

No. 5743-13/23

LC72137, 72137M

Serial Data Input (IN1/IN2) tSU, tHD, tEL, tES, tEH, ≥ 0.75 µs, tLC< 0.75 µs

1. CL: Normal high

2. CL: Normal low

Serial Data Output (OUT) tSU, tHD, tEL, tES, tEH, ≥ 0.75 µs, tDC, tDH< 0.35 µs

1. CL: Normal high

2. CL: Normal low

Note: Since the DO pin is an n-channel open drain circuit, the times for the data to change (tDCand tDH) will differ depending on the value of the pull-up

resistor, printed circuit board capacitance.

No. 5743-14/23

LC72137, 72137M

Serial Data Timing

CL Stopped at the Low Level

CL Stopped at the High Level

Parameter Symbol Pins Conditions min typ max Unit

Data setup time t

SU

DI, CL 0.75 µs

Data hold time t

HD

DI, CL 0.75 µs

Clock low-level time t

CL

CL 0.75 µs

Clock high-level time t

CH

CL 0.75 µs

CE wait time t

EL

CE, CL 0.75 µs

CE setup time t

ES

CE, CL 0.75 µs

CE hold time t

EH

CE, CL 0.75 µs

Data latch change time t

LC

0.75 µs

Data output time

t

DC

DO, CL

These times depend on the pull-up resistance

0.35 µs

t

DH

DO, CE

and the printed circuit board capacitances.

0.35 µs

No. 5743-15/23

LC72137, 72137M

Programmable Divider Structure

Note: * Don’t care.

Sample Programmable Divider Divisor Calculations

1. For a 50 kHz FM step size (DVS = 1, SNS = *: FMIN selected)

• FM RF = 90.0 MHz (IF = +10.7 MHz)
FM VCO = 100.7 MHz
PLL fref = 25 kHz (R0 to R1 = 1, R2 to R3 = 0)

100.7 MHz (FM VCO) ÷ 25 kHz (fref) ÷ 2 (FMIN: divide-by-two prescaler) = 2014 → 07DE (HEX)

2. For a 5 kHz SW step size (DVS = 0, SNS = 1: AMIN high-speed side selected)

• SW RF = 21.75 MHz (IF = +450 kHz)
SW VCO = 22.20 MHz
PLL fref = 5 kHz (R0 = R2 = 0, R1 = R3 = 1)

22.2 MHz (SW VCO) ÷ 5 kHz (fref) = 4440 → 1158 (HEX)

3. For a 9 kHz MW step size (DVS = 0, SNS = 0: AMIN low-speed side selected)

• MW RF = 1008 kHz (IF = +450 kHz)
MW VCO = 1458 kHz
PLL fref = 3 kHz (R0 to R1 = 0, R2 to R3 = 1)
1458 kHz (MW VCO) ÷ 3 kHz (fref) = 486 → 1E6 (HEX)

DVS SNS Input pin Set divisor Actual divisor: N Input frequency range (MHz)
A 1 * FMIN 272 to 65535 Twice the set value 10 to 160
B 0 1 AMIN 272 to 65535 The set value 2 to 40

C 0 0 AMIN 4 to 4095 The set value 0.5 to 10

No. 5743-16/23

LC72137, 72137M

IF Counter Structure

The LC72137 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.

The IF frequency (Fc) is measured by determining how many pulses were input to the IF counter in the stipulated
measurement time, GT.

Fc = (C = Fc × GT) C: count value (number of pulses)

Sample IF Counter Frequency Calculations

1. For a measurement time (GT) of 32 ms and a count value (C) of 53980 (hexadecimal), which is 342,400 (decimal)
IF frequency (Fc) = 342,400 ÷ 32 ms = 10.7 MHz

2. For a measurement time (GT) of 8 ms and a count value (C) of E10 (hexadecimal), which is 3600 (decimal)
IF frequency (Fc) = 3600 ÷ 8 ms = 450 kHz

C

GT

GT1 GT0

Measurement time

Measurement period (GT) (ms) Wait time (t

WU

) (ms)
0 0 4 3 to 4
0 1 8 3 to 4
1 0 16 7 to 8
1 1 32 7 to 8

No. 5743-17/23

LC72137, 72137M

IF Counter Operation

Before starting the IF count, the IF counter must be reset in advance by setting CTE in the serial data to 0.
The IF count is started by changing the CTE bit in the serial data from 0 to 1. The serial data is latched by the LC72137
when the CE pin is dropped from high to low. The IF signal must be supplied to the IFIN pin in the period between the
point the CE pin goes low and the end of the wait time at the latest. Next, the value of the IF count at the end of the
measurement period must be read out during the period CTE is 1. This is because the IF counter is reset when CTE is set
to 0.

Note: When operating the IF counter, the control microcontroller must first check the state of the IF-IC SD (station

detect) signal and only after determining that the SD signal is present turn on IF buffer output and execute an IF
count operation. Auto-search techniques that use only the IF counter are not recommended, since it is possible for
IF buffer leakage output to cause incorrect stops at points where there is no station.
If the auto-search technique is implemented using only the IF counter in combination with an IF-IC without SD
output, sensitivity-degradation mode ( IFS = 0 ) should be selected.

Unlock Detection Timing

1. Unlock Detection Determination Timing
Unlock detection is performed in the reference frequency (fref) period (interval). Therefore, in principle, unlock
determination requires a time longer than the period of the reference frequency. However, immediately after changing
the divisor N (frequency) unlock detection must be performed after waiting at least two periods of the reference
frequency.

No. 5743-18/23

LC72137, 72137M

Figure 1 Unlock Detection Timing

For example, if fref is 1 kHz (and thus the period is 1 ms), after changing the divisor N, the system must wait at least
2 ms before checking for the unlocked state.

Figure 2 Circuit Structure

No. 5743-19/23

LC72137, 72137M

2. Unlock Detection Software

Figure 3

3. When Outputting Unlock Data Using Serial Data Output:
Once the LC72137 detects an unlocked state, it does not reset the unlock data (UL) until the next data output (or data
input) operation is performed. At the data output ① point in Figure 3, although the VCO frequency is stable (locked),
the unlock data remains set to the unlocked state since no data output has been performed since the value of N was
changed. Thus, even though the frequency became stable (locked), from the point of view of the data, the circuit is in
the unlocked state. Therefore, the data output ① immediately following a change to the value of N should be seen as
a dummy data, and the data from the second data output (data output ②) and later outputs should be seen as valid
data.

Lock Determination Flowchart

No. 5743-20/23

LC72137, 72137M

When directly outputting data from the DO pin (set up by the DO pin control data)

Since the DO pin outputs the unlocked state (locked: high, unlocked: low) the timing considerations in the technique
described in the previous section are not necessary. After changing the value of N, the locked state can be determined
after waiting at least two periods of the reference frequency.

Notes on Clock Time Base Usage

When the clock time base output is used, the value of the pull-up resistor for the output pin (BO1) must be at least 100 kΩ.
We recommend the use of a Schmitt input on the receiving controller (microprocessor) to prevent chattering.This is to
avoid degradation of the VCO C/N characteristics when using the built-in low-pass filter transistor to form the loop
filter. Since the clock time base output pin and the low-pass filter transistor ground are the same mode in the IC, the time
base output pin current fluctuations must be suppressed to limit the influence on the low-pass filter.

Other Items

1. Notes on the Phase Comparator Dead Zone

Since correction pulses are output from the charge pump even if the PLL is locked when the charge pump is in the
ON/ON state, the loop can easily become unstable. This point requires special care when designing application
circuits.

The following problems may occur in the ON/ON state.

• Side band generation due to reference frequency leakage

• Side band generation due to both the correction pulse envelope and low frequency leakage

DZ1 DZ0 Dead-zone mode Charge pump Dead zone

0 0 DZA ON/ON – –0 s
0 1 DZB ON/ON –0 s
1 0 DZC OFF/OFF +0 s
1 1 DZD OFF/OFF + +0 s

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LC72137, 72137M

Schemes in which a dead zone is present (OFF/OFF) have good loop stability, but have the problem that acquiring a
high C/N ratio can be difficult. On the other hand, although it is easy to acquire a high C/N ratio with schemes in
which there is no dead zone, it is difficult to achieve high loop stability. Therefore, it can be effective to select DZA
or DZB, which have no dead zone, in applications which require an FM S/N ratio in excess of 90 to 100 dB, or in
which an increased AM stereo pilot margin is desired. On the other hand, we recommend selecting DZC or DZD,
which provide a dead zone, for applications which do not require such a high FM signal-to-noise ratio and in which
either AM stereo is not used or an adequate AM stereo pilot margin can be achieved.

Dead Zone

The phase comparator compares fp to a reference frequency (fr) as shown in Figure 4. Although the characteristics of
this circuit (see Figure 5) are such that the output voltage is proportional to the phase difference ø (line A), a region
(the dead zone) in which it is not possible to compare small phase differences occurs in actual ICs due to internal
circuit delays and other factors (line B). A dead zone as small as possible is desirable for products that must provide
a high S/N ratio.
However, since a larger dead zone makes this circuit easier to use, a larger dead zone is appropriate for popularly­priced products. This is because it is possible for RF signals to leak from the mixer to the VCO and modulate the
VCO in popularly-priced products in the presence of strong RF inputs. When the dead zone is narrow, the circuit
outputs correction pulses and this output can further modulate the VCO and generate beat frequencies with the RF
signal.

Figure 4

Figure 5

2. Notes on the FMIN, AMIN, and IFIN Pins
Coupling capacitors must be placed as close as possible to their respective pin. A capacitance of about 100 pF is
desirable. In particular, if a capacitance of 1000 pF or over is used for the IF pin, the time to reach the bias level will
increase and incorrect counting may occur due to the relationship with the wait time.

3. Notes on IF Counting → SD must be used in conjunction with the IF counting time
When using IF counting, always implement IF counting by having the microprocessor determine the presence of the
IF-IC SD (station detect) signal and turn on the IF counter buffer only if the SD signal is present. Schemes in which
auto-searches are performed with only IF counting are not recommended, since they can stop at points where there is
no signal due to leakage output from the IF counter buffer.

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LC72137, 72137M

4. DO Pin Usage Techniques
In addition to data output mode times, the DO pin can also be used to check for IF counter count completion and for
unlock detection output. Also, an input pin state can be output unchanged through the DO pin and input to the
controller.

5. Power Supply Pins
A capacitor of at least 2000 pF must be inserted between the power supply VDDand VSSpins for noise exclusion.
This capacitor must be placed as close as possible to the VDDand VSSpins.

6. Note on VCO designing
VCO ( local oscillator ) must keep its oscillation even if the control voltage ( Vtune ) goes to 0V. When there is a
possibility of oscillation halt, Vtune must be forcibly set to VCCtemporarily to prevent the PLL from being
deadlocked. ( Deadlock clear circuit )

Pin States at a Power-On Reset

PS. No. 5743-23/23

LC72137, 72137M

This catalog provides information as of July, 1998. Specifications and information herein are subject to change
without notice.

■ No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace
equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of
which may directly or indirectly cause injury, death or property loss.

■ Anyone purchasing any products described or contained herein for an above-mentioned use shall:
➀ Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and

distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all
damages, cost and expenses associated with such use:

➁ Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on

SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees
jointly or severally.

■ Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for
volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied
regarding its use or any infringements of intellectual property rights or other rights of third parties.

Sample Application System

(Using the MFP20 package)