LMX2350/LMX2352
PLLatinum Fractional N RF / Integer N IF
Dual Low Power Frequency Synthesizer
LMX2350 2.5 GHz/550 MHz
LMX2352 1.2 GHz/550 MHz
LMX2352 family features very low current consumption; typically LMX2350 (2.5 GHz) 6.5 mA, LMX2352 (1.2 GHz) 4.75
mA at 3.0V. The LMX2350/2352 are available in a 24-pin
TSSOP and 24-pin CSP surface mount plastic package.
General Description
The LMX2350/2352 is part of a family of monolithic integrated fractional N/ Integer N frequency synthesizers designed to be used in a local oscillator subsystem for a radio
transceiver. It is fabricated using National’s 0.5µ ABiC V
silicon BiCMOS process. The LMX2350/2352 contains dual
modulus prescalers along with modulo 15 or 16 fractional
compensation circuitry in the RF divider. A 16/17 or 32/33
prescale ratio can be selected for the LMX2350, and the
LMX2352 provides 8/9 or 16/17 prescale ratios. The IF
circuitry for both the LMX2350 and LMX2352 contains an 8/9
prescaler, and is fully programmable. Using a fractional N
phase locked loop technique, the LMX2350 /52 can generate very stable low noise control signals for UHF and VHF
voltage controlled oscillators (VCOs).
For the RF PLL, a highly flexible 16 level programmable
charge pump supplies output current magnitudes from
100µA to 1.6mA. Two uncommitted CMOS outputs can be
used to provide external control signals, or configured to
FastLock™ mode. Serial data is transferred into the
LMX2350/2352 via a three wire interface (Data, LE, Clock).
Supply voltage can range from 2.7 V to 5.5 V. The LMX2350/
Features
n 2.7 V to 5.5 V operation
n Low current consumption
LMX2350: Icc = 6.75mA typ at 3v
LMX2352: Icc = 5.00mA typ at 3v
n Programmable or logical power down mode
Icc = 5 µA typ at 3v
n Modulo 15 or 16 fractional RF N divider supports ratios
of 1, 2, 3, 4, 5, 8, 15, or 16
n Programmable charge pump current levels
RF 100µA to 1.6mA in 100µA steps
IF 100µA or 800 µA
n Digital filtered lock detect
Applications
n Portable wireless communications (PCS/PCN, cordless)
n Dual mode cellular telephone systems
n Zero blind slot TDMA systems
n Spread spectrum communication systems (CDMA)
n Cable TV Tuners (CATV)
Block Diagram
DS100831-1
© 2001 National Semiconductor Corporation
DS100831
www.national.com
LMX2350/LMX2352 PLLatinum Fractional N RF / Integer N IF Dual Low Power Frequency
Synthesizer
March 2001
LMX2350/LMX2352
Connection Diagrams
DS100831-2
Order Number LMX2350TM or LMX2352TM
NS Package Number MTC24
DS100831-22
Pin Descriptions
Pin No.
for CSP
Package
Pin No.
for
TSSOP
package
24
1
Pin Name
I/O
Description
1
OUT0
O
Programmable CMOS output. Level of the output is controlled by IF_N [17] bit.
2
VccRF
-
RF PLL power supply voltage input. Must be equal to VccIF. May range from 2.7 V to
5.5 V. Bypass capacitors should be placed as close as possible to this pin and be
connected directly to the ground plane.
2
3
VpRF
-
Power supply for RF charge pump. Must be ≥VccRF and VccIF.
3
4
CPoRF
O
RF charge pump output. Connected to a loop filter for driving the control input of an
external VCO.
4
5
GND
-
Ground for RF PLL digital circuitry.
5
6
fin RF
I
RF prescaler input. Small signal input from the VCO.
6
7
fin RF
I
RF prescaler complimentary input. A bypass capacitor should be placed as close as
possible to this pin and be connected directly to the ground plane.
7
8
GND
-
8
9
OSCx
I/O
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Ground for RF PLL analog circuitry.
Dual mode oscillator output or RF R counter input. Has a Vcc/2 input threshold when
configured as an input and can be driven from an external CMOS or TTL logic gate.
Can also be configured as an output to work in conjunction with OSCin to form a
crystal oscillator. (See functional description 1.1 and programming description 3.1.)
2
(Continued)
Pin No.
for CSP
Package
Pin No.
for
TSSOP
package
9
10
OSCin
I
Oscillator input which can be configured to drive both the IF and RF R counter inputs
or only the IF R counter depending on the state of the OSC programming bit. (See
functional description 1.1 and programming description 3.1.)
10
11
FoLD
O
Multiplexed output of N or R divider and RF/IF lock detect. Active High/Low CMOS
output except in analog lock detect mode. (See programming description 3.1.5.)
11
12
RF_EN
I
RF PLL Enable. Powers down RF N and R counters, prescaler, and will TRI-STATE ®
the charge pump output when LOW. Bringing RF_EN high powers up RF PLL
depending on the state of RF_CTL_WORD. (See functional description 1.9.)
12
13
IF_EN
I
IF PLL Enable. Powers down IF N and R counters, prescaler, and will TRI-STATE the
charge pump output when LOW. Bringing IF_EN high powers up IF PLL depending on
the state of IF_CTL_WORD. (See functional description 1.9.)
13
14
CLOCK
I
High impedance CMOS Clock input. Data for the various counters is clocked into the
24 - bit shift register on the rising edge.
14
15
DATA
I
Binary serial data input. Data entered MSB first. The last two bits are the control bits.
High impedance CMOS input.
15
16
LE
I
Load enable high impedance CMOS input. Data stored in the shift registers is loaded
into one of the 4 internal latches when LE goes HIGH. (See functional description 1.7.)
16
17
GND
-
Ground for IF analog circuitry.
17
18
fin IF
I
IF prescaler complimentary input. A bypass capacitor should be placed as close as
possible to this pin and be connected directly to the ground plane.
18
19
fin IF
I
IF prescaler input. Small signal input from the VCO.
19
20
GND
-
Ground for IF digital circuitry.
20
21
CPoIF
O
IF charge pump output. For connection to a loop filter for driving the input of an
external VCO.
21
22
VpIF
-
Power supply for IF charge pump. Must be ≥ VccRF and VccIF.
22
23
VccIF
-
IF power supply voltage input. Must be equal to VccRF . Input may range from 2.7 V to
5.5 V. Bypass capacitors should be placed as close as possible to this pin and be
connected directly to the ground plane.
23
24
OUT1
O
Programmable CMOS output. Level of the output is controlled by IF_N [18] bit.
Pin Name
I/O
Description
3
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LMX2350/LMX2352
Pin Descriptions
LMX2350/LMX2352
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Value
Parameter
Symbol
Min
Max
Units
VccRF
-0.3
6.5
V
VccIF
-0.3
6.5
V
VpRF
-0.3
6.5
V
VpIF
-0.3
6.5
V
Voltage on any pin with GND = 0 volts
Vi
-0.3
Vcc + 0.3
V
Storage Temperature Range
Ts
-65
Lead Temperature (Solder 4 sec.)
TL
Power Supply Voltage
Typ
+150
C˚
+260
C˚
Recommended Operating Conditions
Value
Parameter
Power Supply Voltage
Symbol
Min
Max
Units
VccRF
2.7
5.5
V
VccIF
VccRF
VccRF
V
VpRF
Vcc
5.5
V
VpIF
Vcc
5.5
V
TA
-40
+ 85
C
Operating Temperature
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage
to the device may occur. Operating Ratings indicate conditions for which the
device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the
Electrical Characteristics. The guaranteed specifications apply only for the
test conditions listed.
Electrical Characteristics
Symbol
Typ
Note 2: This Device is a high performance RF integrated circuit with an ESD
rating < 2 KV and is ESD sensitive. Handling and assembly of this device
should only be done at ESD-free workstations.
(VccRF = VccIF = VPRF = VPIF = 3.0V; −40˚ C < TA < 85˚ C except as specified)
Parameter
Conditions
Min
Typ
Max
Units
General
Icc
Power Supply Current
ICC-PWDN
Power Down Current
fin RF
RF Operating
LMX2350
RF and IF,
Vcc = 2.7V to 5.5V
6.5
8.75
mA
LMX2352
RF and IF,
Vcc = 2.7V to 5.5V
4.75
6.0
mA
LMX2350/52
IF only, Vcc = 2.7V to 5.5V
1
2.2
mA
20
µA
LMX2350
Prescaler = 32 (Note 3)
1.2
2.5
GHz
Prescaler = 16 (Note 3)
0.5
1.2
GHz
Prescaler = 16 (Note 3)
0.5
1.2
GHz
Prescaler = 8 (Note 3)
0.25
0.5
GHz
10
550
MHz
No load on OSCx (Note 3)
2
50
MHz
With resonator load on
OSCx (Note 3)
2
20
MHz
RF_EN = IF_EN = LOW
Frequency
LMX2352
fin IF
IF Operating Frequency
fOSC
Oscillator Frequency
5
fφ
Phase Detector Frequency
RF and IF
10
MHz
Pfin RF
RF Input Sensitivity
2.7V≤VCC ≤3.0V
−15
0
dBm
3.0V≤VCC ≤5.5V
−10
0
dBm
Pfin IF
IF Input Sensitivity
2.7 V≤VCC≤ 5.5V
−10
0
dBm
VOSC
Oscillator Sensitivity
OSCin, OSCx
0.5
VCC
VPP
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4
(VccRF = VccIF = VPRF = VPIF = 3.0V; −40˚ C < TA < 85˚ C except as
specified) (Continued)
All Min/Max specifications are guaranteeed by design, or test, or statistical methods.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Charge Pump
ICPo-source
RF
ICPo-sink RF
ICPo-source
RF Charge Pump
Output Current (see
Programming
Description 3.2.2)
VCPo Vp/2, RF_CP_WORD = 0000
IF Charge Pump Output
Current (see
Programming
Description 3.1.4)
VCPo = Vp/2, CP_GAIN_8 = 0
−100
µA
VCPo = Vp/2, RF_CP_WORD = 0000
100
µA
VCPo = Vp/2, RF_CP_WORD = 1111
−1.6
mA
RF
ICPo-sink RF
ICPo-source
IF
ICPo-sink IF
ICPo-source
VCPo = Vp/2, RF_CP_WORD = 1111
1.6
mA
−100
µA
VCPo = Vp/2, CP_GAIN_8 = 0
100
µA
VCPo = Vp/2, CP_GAIN_8 = 1
−800
µA
VCPo = Vp/2, CP_GAIN_8 = 1
800
µA
IF
ICPo-sink IF
ICPo-Tri
Charge Pump
TRI-STATE Current
0.5 ≤ VCPo ≤ Vp - 0.5
-40˚ C < TA < 85˚ C
ICPo-sink
vs.
ICPo-source
CP Sink vs. Source
Mismatch
VCPo = Vp/2
TA = 25˚ C
RFICPo
= 400 µA - 1.6 mA
ICPo vs.
VCPo
CP Current vs. Voltage
0.5 ≤ VCPo ≤ Vp 0.5
TA = 25˚ C
RFICPo
= 800 µA - 1.6 mA
ICPo vs. T
CP Current vs
Temperature
VCPo = Vp/2
-40˚ C < TA < 85˚ C
-2.5
2.5
nA
3
10
%
4
15
%
8
%
Digital Interface
VIH
High-level Input Voltage
(Note 4)
VIL
Low-level Input Voltage
(Note 4)
IIH
High-level Input Current
VIH = VCC = 5.5 V, (Note 4)
−1.0
IIL
Low-level Input Current
VIL = 0, VCC = 5.5 V, (Note 4)
−1.0
IIH
Oscillator Input Current
VIH = VCC = 5.5 V
IIL
Oscillator Input Current
VIL = 0, VCC = 5.5 V
−100
µA
VOH
High-level Output
Voltage
IOH = −500 µA
VCC −0.4
V
VOL
High-level Output
Voltage
IOL = 500 µA
0.8 Vcc
V
0.2 Vcc
V
1.0
µA
1.0
µA
100
µA
0.4
V
MICROWIRE Timing
tCS
Data to Clock Setup
Time
See Data Input Timing
50
ns
tCH
Data to Clock Hold
Time
See Data Input Timing
10
ns
tCWH
Clock Pulse Width High
See Data Input Timing
50
ns
tCWL
Clock Pulse Width Low
See Data Input Timing
50
ns
tES
Clock to Load Enable
Set Up Time
See Data Input Timing
50
ns
tEW
Load Enable Pulse
Width
See Data Input Timing
50
ns
Note 3: Minimum operating frequencies are not production tested - only characterized.
Note 4: except fin, OSCin and OSCx
5
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LMX2350/LMX2352
Electrical Characteristics
LMX2350/LMX2352
Charge Pump Current Specification Definitions
DS100831-7
I1 = CP sink current at VDo = Vp − ∆V
I2 = CP sink current at VDo = Vp/2
I3 = CP sink current at VDo = ∆V
I4 = CP source current at VDo = Vp − ∆V
I5 = CP source current at VDo = Vp/2
I6 = CP source current at VDo = ∆V
∆V = Voltage offset from positive and negative rails. Dependent on VCO tuning range relative to VCC and ground. Typical values are between 0.5V and 1.0V.
Note 5: IDo vs VDo = Charge Pump Output Current magnitude variation vs Voltage = [1⁄2 * {||1| − ||3|}]/[1⁄2 * {||1| + ||3|}] * 100% and [1⁄2 * {||4| − ||6|}]/[1⁄2 * {||4| +
||6|}] * 100%
Note 6: IDo-sink vs IDo-source = Charge Pump Output Current Sink vs Source Mismatch = [||2| − ||5|]/[1⁄2 * {||2| + ||5|}] * 100%
Note 7: IDo vs TA = Charge Pump Output Current magnitude variation vs Temperature = [||2 @ temp| − ||2 @ 25˚C|]/||2 @ 25˚C| * 100% and [||5 @ temp| − ||5 @
25˚C|]/||5 @ 25˚C| * 100%
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6
LMX2350/LMX2352
RF Sensitivity Test Block Diagram
DS100831-8
Note: N = 10,000 R = 50 P = 32
Note: Sensitivity limit is reached when the error of the divided RF output, FoLD, is ≥ 1 Hz.
Typical Performance Characteristics
ICC vs VCC
LMX2350
ICC vs VCC
LMX2352
DS100831-9
ICPO TRI-STATE vs
CPO Voltage
DS100831-10
Charge Pump Current vs CPO Voltage
RF_CP_WORD = 0000 and 0111
IF CP_GAIN_8 = 0 and 1
DS100831-11
DS100831-12
7
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LMX2350/LMX2352
Typical Performance Characteristics
(Continued)
Charge Pump Current vs CPO Voltage
RF_CP_WORD = 0011 and 1111
Sink vs Source Mismatch
(See (Note 6) under Charge Pump Current
Specification Definitions)
DS100831-13
DS100831-14
RF Input Impedance
VCC = 2.7V to 5.5V, fIN = 50 MHz to
3 GHz (fIN Capacitor = 100 pF)
IF Input Impedance
VCC = 2.7V to 5.5V, fIN = 10 MHz to
1 GHz (fIN Capacitor = 100 pF)
DS100831-15
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DS100831-16
8
(Continued)
LMX2350 RF Sensitivity vs Frequency
LMX2352 RF Sensitivity vs Frequency
DS100831-18
DS100831-17
IF Input Sensitivity vs Frequency
LMX2350/LMX2352
Typical Performance Characteristics
Oscillator Input Sensitivity vs Frequency
DS100831-19
DS100831-20
LMX2350 VP Voltage vs VP Load Current in Vdoubler
Mode, T = 25˚C
DS100831-21
9
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LMX2350/LMX2352
and a 10 bit B Counter. The LMX2350 is capable of operating from 500 MHz to 1.2 GHz with the 16/17 prescaler
offering a continuous integer divide range from 272 to
16399, and 1.2 GHz to 2.5 GHz with the 32/33 prescaler
offering a continuous integer divide range from 1056 to
32767. The LMX2352 RF N counter is 18 bits with 14 bits
integer divide and 4 bits fractional. The integer part is configured as a 4 bit A Counter and a 10 bit B Counter. The
LMX2352 is capable of operating from 250 MHz to 500 MHz
with the 8/9 prescaler offering a continuous integer divide
range from 72 to 8199, and 500MHz to 1.2 GHz with 16/17
prescaler offering a continuous integer divide range from 272
to 16383. The RF counters for the LMX2350 family also
contain fractional compensation, programmable in either
1/15 or 1/16 modes. Both LMX2350 and LMX2352 IF N
counters are 15 bit integer dividers configured with a 3 bit A
Counter and a 12 bit B Counter offering a continuous integer
divide range from 56 to 32,767 over the frequency range of
10 MHz to 550 MHz. The IF N counters do not include
fractional compensation.
Functional Description
1.0 General
The basic phase-lock-loop (PLL) configuration consists of a
high-stability crystal reference oscillator, a frequency synthesizer such as the National Semiconductor LMX2350/52, a
voltage controlled oscillator (VCO), and a passive loop filter.
The frequency synthesizer includes a phase detector, current mode charge pump, as well as programmable reference
[R] and feedback [N] frequency dividers. The VCO frequency
is established by dividing the crystal reference signal down
via the R counter to obtain a frequency that sets the comparison frequency. This reference signal, fr, is then presented to the input of a phase/frequency detector and compared with another signal, fp, the feedback signal, which was
obtained by dividing the VCO frequency down by way of the
N counter and fractional circuitry. The phase/frequency detector’s current source outputs pump charge into the loop
filter, which then converts the charge into the VCO’s control
voltage. The phase/frequency comparator’s function is to
adjust the voltage presented to the VCO until the feedback
signal’s frequency (and phase) match that of the reference
signal. When this ’phase-locked’ condition exists, the RF
VCO’s frequency will be N+F times that of the comparison
frequency, where N is the integer divide ratio and F is the
fractional component. The fractional synthesis allows the
phase detector frequency to be increased while maintaining
the same frequency step size for channel selection. The
division value N is thereby reduced giving a lower phase
noise referred to the phase detector input, and the comparison frequency is increased allowing faster switching times.
1.3.1 Prescaler
The RF and IF inputs to the prescaler consist of fin and /fin;
which are complimentary inputs to differential pair amplifiers.
The complimentary inputs are internally coupled to ground
with a 10 pF capacitor. These inputs are typically AC coupled
to ground through external capacitors as well. The input
buffer drives the A counter’s ECL D-type flip flops in a dual
modulus configuration. A 16/17 or 32/33 prescale ratio can
be selected for the LMX2350, and the lower frequency
LMX2352 provides 8/9 or 16/17 prescale ratios. The IF
circuitry for both the LMX2350 and LMX2352 contain an 8/9
prescaler. The prescaler clocks the subsequent CMOS flipflop chain comprising the fully programmable A and B
counters.
1.1 Reference Oscillator Inputs
The reference oscillator frequency for the RF and IF PLL’s is
provided by either an external reference through the OSCin
pin and OSCx pin, or an external crystal resonator across
the OSCin and OSCx pins. OSCin/OSCx block can operate
to 50MHz with an input sensitivity of 0.5Vpp. The OSC bit
(see programming description 3.1.1), selects whether the
oscillator input pins OSCin and OSCx drive the IF and RF R
counters separately (Low) or by a common input signal path
(Hi). The common OSC mode allows the user to form a local
crystal oscillator circuit or drive the OSCin pin from an external signal source. When a crystal resonator is connected
between OSCin and OSCx along with 2 external capacitors
to form a crystal oscillator both reference chains are driven
simultaneously. When a TCXO is connected only at the
OSCin input pin and not at the OSCx pin, the TCXO drives
both IF R counter and RF R counter. When configured as
separate inputs, the OSCin pin drives the IF R counter while
the OSCx drives the RF R counter. The inputs have a Vcc/2
input threshold and can be driven from an external CMOS or
TTL logic gate.
1.3.2 Fractional Compensation
The fractional compensation circuitry of the LMX2350 and
LMX2352 RF dividers allow the user to adjust the VCO’s
tuning resolution in 1/16 or 1/15 increments of the phase
detector comparison frequency. A 4 bit register is programmed with the fractions desired numerator, while another
bit selects between fractional 15 and 16 modulo base denominator (see programming description 4.2.4). An integer
average is accomplished by using a 4 bit accumulator. A
variable phase delay stage compensates for the accumulated integer phase error, minimizing the charge pump duty
cycle, and reducing spurious levels. This technique eliminates the need for compensation current injection in to the
loop filter. Overflow signals generated by the accumulator
are equivalent to 1 full VCO cycle, and result in a pulse
swallow.
1.4 Phase/Frequency Detector
The RF and IF phase(/frequency) detectors are driven from
their respective N and R counter outputs. The maximum
frequency at the phase detector inputs is about 10 MHz for
some high frequency VCO due to the minimum continuous
divide ratio of the dual modulus prescaler. For example if the
phase detector frequency exceeds 2.37 MHz, there are
higher chances of running into illegal divide ratios, because
the mimimum continuous divide ratio of the LMX2350 with
32/33 prescaler is 1056. The phase detector outputs control
the charge pumps. The polarity of the pump-up or pumpdown control is programmed using RF_PD_POL or IF_PD_POL depending on whether RF/IF VCO characteristics are
positive or negative (see programming descriptions 3.1.4
1.2 Reference Dividers (R Counters)
The RF and IF R Counters are clocked through the oscillator
block either separately or in common. The maximum frequency is 50MHz. Both R Counters are 15 bit CMOS
counters with a divide range from 3 to 32,767. (See programming description 3.1.3.)
1.3 Programmable Dividers (N Counters)
The RF and IF N Counters are clocked by the small signal fin
RF and fin IF input pins respectively. The LMX2350 RF N
counter is 19 bits with 15 bits integer divide and 4 bits
fractional. The integer part is configured as a 5 bit A Counter
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10
signal is also selectable. The lock detect output is always low
when the PLL is in power down mode. See programming
descriptions 3.1.5, 4.6 - 4.8 for more details.
(Continued)
and 3.2.2). The phase detector also receives a feedback
signal from the charge pump, in order to eliminate dead
zone.
1.9 Power Control
Each PLL is individually power controlled by device enable
pins or MICROWIRE power down bits. The enable pins
override the power down bits except for the V2_EN bit. The
RF_EN pin controls the RF PLL; IF_EN pin controls the IF
PLL. When both pins are high, the power down bits determine the state of power control (see programming description 3.2.1.2). Activation of any PLL power down mode results
in the disabling of the respective N counter and de-biasing of
its respective Fin input (to a high impedance state). The R
counter functionality also becomes disabled when the power
down bit is activated. The reference oscillator block powers
down and the OSCin pin reverts to a high impedance state
when both RF and IF enable pins or power down bit’s are
asserted, unless the V2_EN bit (RF_R[22]) is high. Power
down forces the respective charge pump and phase comparator logic to a TRI-STATE condition. A power down
counter reset function resets both N and R counters. Upon
powering up the N counter resumes counting in “close”
alignment with the R counter (The maximum error is one
prescaler cycle). The MICROWIRE control register remains
active and capable of loading and latching in data during all
of the power down modes.
1.5 Charge Pump
The phase detector’s current source outputs pump charge
into an external loop filter, which then converts the charge
into the VCO’s control voltage. The charge pumps steer the
charge pump output, CPo, to Vcc (pump-up) or ground
(pump-down). When locked, CPo is primarily in a
TRI-STATE ® mode with small corrections. The RF charge
pump output current magnitude is programmable from 100
µA to 1.6 mA in 100 µA steps as shown in table in programming description 3.2.2. The IF charge pump is set to either
100µA or 800µA levels using bit IF_R [19] (see programming
description 3.1.4).
1.6 Voltage Doubler
The VpRF pin is normally driven from an external power
supply over a range of Vcc to 5.5v to provide current for the
RF charge pump circuit. An internal voltage doubler circuit
connected between the Vcc and VpRF supply pins alternately allows Vcc = 3v ( ± 10%) users to run the RF charge
pump circuit at close to twice the Vcc power supply voltage.
The voltage doubler mode is enabled by setting the V2_EN
bit (RF_R [22]) to a HIGH level. The voltage doubler’s
charge pump driver originates from the RF oscillator input
(OSCx). The device will not totally powerdown until the
V2_EN bit is programmed low. The average delivery current
of the doubler is less than the instantaneous current demand
of the RF charge pump when active and is thus not capable
of sustaining a continuous out of lock condition. A large
external capacitor connected to VpRF is therefore needed to
control power supply droop when changing frequencies. Refer to the application note AN-1119 for more details.
1.7 MICROWIRE™ Serial Interface
The programmable functions are accessed through the MICROWIRE serial interface. The interface is made of 3 functions: clock, data and latch enable (LE). Serial data for the
various counters is clocked in from data on the rising edge of
clock, into the 24- bit shift register. Data is entered MSB first.
The last two bits decode the internal register address. On the
rising edge of LE, data stored in the shift register is loaded
into one of the 4 appropriate latches (selected by address
bits). A complete programming description is included in the
following sections.
1.8 Fo/LD Multifunction Output
The Fo/LD output pin can deliver several internal functions
including analog/digital lock detects, and counter outputs.
See programming description 3.1.5 for more details.
1.8.1 Lock Detect
A digital filtered lock detect function is included with each
phase detector through an internal digital filter to produce a
logic level output available on the Fo/LD output pin if selected. The lock detect output is high when the error between
the phase detector inputs is less than 15 nsec for 5 consecutive comparison cycles. The lock detect output is low when
the error between the phase detector outputs is more than
30 nsec for one comparison cycle. An analog lock detect
11
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LMX2350/LMX2352
Functional Description
LMX2350/LMX2352
Programming Description
2.0 INPUT DATA REGISTER
The descriptions below describe the 24-bit data register loaded through the MICROWIRE Interface. The data register is used to
program the 15-bit IF_R counter register, and the 15-bit RF_R counter register, the 15-bit IF_N counter register, and the 19-bit
RF_N counter register. The data format of the 24-bit data register is shown below. The control bits CTL [1:0] decode the internal
register address. On the rising edge of LE, data stored in the shift register is loaded into one of the 4 appropriate latches (selected
by address bits). Data is shifted in MSB first
MSB
LSB
DATA [21:0]
CTL [1:0]
23
2
1
0
2.1 Register Location Truth Table
CTL [1:0]
DATA Location
1
0
0
0
IF_R register
0
1
IF_N register
1
0
RF_R register
1
1
RF_N register
2.2 Register Content Truth Table
First Bit
IF_R
REGISTER BIT LOCATION
23
22
21 20 19
OSC
FRAC_16
FoLD
IF_N
IF_CTL_WORD
RF_R DLL_MODE
RF_N
18
17
IF_CP_WORD
3
2
1 0
0 0
IF_NB_CNTR
RF_CP_WORD
RF_CTL_WORD
4
IF_R_CNTR
CMOS
V2_EN
Last Bit
16 15 14 13 12 11 10 9 8 7 6 5
IF_NA_CNTR 0 1
RF_R_CNTR
RF_NB_CNTR
1 0
RF_NA_CNTR
FRAC_CNTR
1 1
3.0 PROGRAMMABLE REFERENCE DIVIDERS
3.1 IF_R Register
If the Control Bits (CTL [1:0]) are 0 0, when LE is transitioned high data is transferred from the 24-bit shift register into a latch
which sets the IF PLL 15-bit R counter divide ratio. The divide ratio is programmed using the bits IF_R_CNTR as shown in table
3.1.3. The ratio must be ≥ 3. The IF_CP_WORD [1:0], programs the IF charge pump magnitude and polarity shown in 3.1.4. The
OSC bit is used to enable the crystal oscillator mode. FoLD [2:0] is used to set the function of the Lock Detect output (pin 11),
according to table 3.1.3.
MSB
LSB
OSC
FRAC_16
FoLD [2:0]
23
22
21
19
IF_CP_WORD [1:0]
IF_R_CNTR [14:0]
0
0
18
16
1
0
17
2
3.1.1 OSC
(IF_R[23])
The OSC bit, IF_R [23], selects whether the oscillator input pins OSCin and OSCx drive the IF and RF R counters separately or
by a common input signal path. When the OSC bit = 1, a crystal resonator can be connected between OSCin and OSCx together
with 2 capacitors to form a crystal oscillator. When OSC = 0 , the OSCin pin drives the IF R counter while the OSCx drives the
RF R counter.
3.1.2 FRAC_16
(IF_R[22])
The FRAC_16 bit, IF_R [22], is used to set the fractional compensation at either 1/16 and 1/15 resolution. When FRAC-16 is set
to one, the fractional modulus is set to 1/16 resolution, and FRAC_16 = 0 corresponds to 1/15 (See section 4.2.4).
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12
(Continued)
3.1.3 15-BIT PROGRAMMABLE REFERENCE DIVIDER RATIO (R COUNTER)
(IF_R[2]-[16])
IF_R_CNTR/RF_R_CNTR
Divide Ratio
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
3
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
4
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
32,767
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Notes: Divide ratio: 3 to 32,767 (Divide ratios less than 3 are prohibited).
RF_R_CNTR/IF_R_CNTR These bits select the divide ratio of the programmable reference dividers.
3.1.4 IF_CP_WORD
(IF_R[17]-[18])
IF_CP_WORD
(IF_R [17] - [18] )
CP_GAIN_8
IF_PD_POL
BIT
LOCATION
FUNCTION
0
1
CP_GAIN_8
IF_R [18]
IF Charge Pump Current Gain
1X
8X
IF_PD_POL
IF_R [17]
IF Phase Detector Polarity
Negative
Positive
CP_GAIN_8 is used to toggle the IF charge pump current magnitude between 1x mode (100 uA typ) and 8x mode (800uA typ).
IF_PD_POL is set to one when IF VCO characteristics are positive. When IF VCO frequency decreases with increasing control
voltage IF_PD_POL should set to zero.
3.1.5 FoLD* Programming Truth Table
(IF_R[19]-[21])
FoLD
Fo/LD OUTPUT STATE
000
IF and RF Analog Lock Detect (Open Drain)
100
IF Digital Lock Detect
010
RF Digital Lock Detect
110
IF and RF Digital Lock Detect
001
IF R counter
101
IF N counter
011
RF R counter
111
RF N counter
*FoLD - Fout/Lock Detect PROGRAMMING BITS
3.2 RF_R Register
If the Control Bits (CTL [1:0]) are 1 0, data is transferred from the 24-bit shift register into the RF_R register latch which sets the
RF PLL 15-bit R counter divide ratio. The divide ratio is programmed using the RF_R_CNTR word as shown in table 3.1.3. The
divide ratio must be ≥ 3. The bits used to control the voltage doubler (V2_EN) and RF Charge Pump (RF_CP_WORD) are
detailed in 3.2.2.
MSB
DLL_MODE
23
LSB
V2_EN
22
RF_CP_WORD [4:0]
21
RF_R_CNTR [14:0]
17
13
16
2
1
0
1
0
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LMX2350/LMX2352
Programming Description
LMX2350/LMX2352
Programming Description
(Continued)
3.2.1 (RF_R [22 - 23] )
DLL_MODE
V2_EN
BIT
LOCATION
FUNCTION
0
1
DLL_MODE
RF_R [23]
Delay Line Loop Calibration
Mode
Slow
Fast
V2_EN
RF_R [22]
RF_Voltage Doubler Enable
Disabled
Enabled
1. V2_EN bit when set high enables the voltage doubler for the RF Charge Pump supply.
2. DLL_MODE bit should be set to one for normal usage.
3.2.2 RF_CP_WORD
(RF_R[17]-[21])
CP_8X
CP_4X
CP_2X
CP_1X
RF_PD_POL
RF_PD_POL ( RF_R[17] ) should be set to one when RF VCO characteristics are positive. When RF VCO frequency decreases
with increasing control voltage RF_PD_POL should be set to zero.
CP_1x, CP_2x, CP_4x, and CP_8x are used to step the RF Charge Pump output current magnitude from 100 uA to 1.6 mA in
100uA steps as shown in the table below.
RF Charge Pump Output Truth Table
ICPo uA (typ)
CP8x
CP4x
CP2x
CP1x
RF_R[21]
RF_R[20]
RF_R[19]
RF_R[18]
100
0
0
0
0
200
0
0
0
1
300
0
0
1
0
400
0
0
1
1
-
-
-
-
-
900
1
0
0
0
-
-
-
-
-
1600
1
1
1
1
4.0 PROGRAMMABLE DIVIDERS (N COUNTERS)
4.1 IF_N Register
If the Control Bits (CTL [1:0]) are 01, data is transferred from the 24-bit shift register into the IF_N register latch which sets the
PLL 15 bit programmable N counter value and various control functions. The IF_N counter consists of the 3-bit swallow counter
(A counter), and the 12 bit programmable counter (B counter). Serial data format is shown below in tables 4.1.2 and 4.1.3. The
divide ratio (IF_NB_CNTR) must be ≥3. The divide ratio is programmed using the bits IF_N_CNTR as shown in tables 4.1.2 and
4.1.3. The divide ratio must be ≥56. The CMOS [3:0] bits program the 2 CMOS outputs detailed in section 4.4.
MSB
LSB
IF_CTL_WORD [2:0]
23
CMOS [3:0]
21
4.1.1 IF_CTL_WORD
20
IF_NB_CNTR [11:0]
17
16
4
2
(IF_R[21]-[23])
MSB
IF_CNT_RST
LSB
PWDN_IF
Note: See section 4.2.1.2 for IF control word truth table.
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IF_NA_CNTR [2:0]
5
14
PWDN_MODE
0
1
1
0
LMX2350/LMX2352
Programming Description
(Continued)
4.1.2 3-BIT IF SWALLOW COUNTER DIVIDE RATIO (IF A COUNTER)
Swallow Count
(IF_N[2]−[4])
IF_NA_CNTR
(A)
2
1
0
0
0
0
0
1
0
0
1
-
-
-
-
7
1
1
1
Note: Swallow Counter Value: 0 to 7
IF_NB_CNTR ≥ IF_NA_CNTR
Minimum continuous count = 56 ( A=0, B=7)
4.1.3 12-BIT IF PROGRAMMABLE COUNTER DIVIDE RATIO (IF B COUNTER)
(IF_N[5]-[16])
IF_NB_CNTR
Divide Ratio
11
10
9
8
7
6
5
4
3
2
1
0
3
0
0
0
0
0
0
0
0
0
0
1
1
4
0
0
0
0
0
0
0
0
0
1
0
0
-
-
-
-
-
-
-
-
-
-
-
-
-
4,095
1
1
1
1
1
1
1
1
1
1
1
1
Note: Divide ratio: 3 to 4095 (Divide ratios less than 3 are prohibited)
IF_NB_CNTR ≥ IF_NA_CNTR
N divider continuous integer divide ratio 56 to 32,767.
4.2 RF_N Register
If the control bits (CTL[2:0]) are 11, data is transferred from the 24-bit shift register into the RF_N register latch which sets the RF
PLL 19 bit programmable N counter register and various control functions. The RF N counter consists of the 5-bit swallow counter
(A counter) the 10 bit programmable counter (B counter), and 4 bit fractional counter. Serial data format is shown below. The
divide ratio (RF_NB_CNTR) must be ≥3, and must be ≥ the swallow counter value + 2; RF_NB_CNTR≥ ( RF_NA_CNTR+2).
MSB
LSB
RF_CTL_WORD [2:0]
23
RF_NB_CNTR [9:0]
21
4.2.1.1 RF_CTL_WORD
20
RF_NA_CNTR [4:0]
11
FRAC_CONT [3:0]
10
6
5
2
1
1
1
0
(RF_N[21]-[23])
MSB
LSB
RF_CNT_RST
PWDN_RF
PRESC_SEL
4.2.1.2 RF/IF Control Word Truth Table
BIT
FUNCTION
0
1
IF_CNT_RST/RF_CNT_RST
IF/RF counter reset
Normal Operation
Reset
PWDN_IF/PWDN_RF
IF/RF power down
Powered up
Powered down
PWDN_MODE
PRESC
LMX2350
Power down mode select
Asynchronous power down
Synchronous power down
Prescaler Modulus select
16/17
(0.5 to 1.2 GHz operation)
32/33
(1.2 to 2.5 GHz operation)
8/9
(0.25 to 0.5 GHz operation)
16/17
(0.5 to 1.2 GHz operation)
LMX2352
pump and phase comparator logic to a TRI-STATE condition.
The MICROWIRE control register remains active and capable of loading and latching in data during all of the power
down modes.
Both synchronous and asynchronous power down modes
are available with the LMX2350 family in order to adapt to
different types of applications. The power down mode bit
IF_N[21] is used to select between synchronous and asynchronous power down. The MICROWIRE control register
remains active and capable of loading and latching in data
during all of the power down modes.
The Counter Reset enable bit when activated allows the
reset of both N and R counters. Upon powering up, the N
counter resumes counting in ’close’ alignment with the R
counter (the maximum error is one prescaler cycle).
Activation of the PLL power down bits result in the disabling
of the respective N counter divider and de-biasing of its
respective fin inputs (to a high impedance state). The respective R counter functionality also becomes disabled
when the power down bit is activated. The OSCin pin reverts
to a high impedance state when both RF and IF power down
bits are asserted. Power down forces the respective charge
15
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LMX2350/LMX2352
Programming Description
4.2.2 5-BIT RF SWALLOW COUNTER DIVIDE RATIO
(RF A COUNTER)
(RF_N[6]-[10])
(Continued)
Synchronous Power down Mode
Swallow Count
One of the PLL loops can be synchronously powered down
by first setting the power down mode bit HIGH (IF_N[21] = 1)
and then asserting its power down bit (IF_N[22] or RF_N[22]
= 1). The power down function is gated by the charge pump.
Once the power down bit is loaded, the part will go into
power down mode upon the completion of a charge pump
pulse event.
Asynchronous Power down Mode
One of the PLL loops can be asynchronously powered down
by first setting the power down mode bit LOW (IF_N[21] = 0)
and then asserting its power down bit (IF_N[22] or RF_N[22]
= 1). The power down function is NOT gated by the charge
pump. Once the power down bit is loaded, the part will go
into power down mode immediately.
Prescaler select is used to set the RF prescaler. The
LMX2350 is capable of operating from 500 MHz to 1.2 GHz
with the 16/17 prescaler, and 1.2 GHz to 2.5 GHz with the
32/33 prescaler selection. The LMX2352 is capable of operating from 250 MHz to 500 MHz with the 8/9 prescaler, and
500MHz to 1.2GHz with 16/17 prescaler selection.
RF_NA_CNTR
(A)
4
3
2
1
0
0
0
0
0
0
0
1
0
0
0
0
1
-
-
-
-
-
-
31
1
1
1
1
1
Note: Swallow Counter Value LMX2350: 0 to 31; LMX2352: 0 to 15
RF_NB_CNTR ≥ RF_NA_CNTR + 2
4.2.3 10-BIT RF PROGRAMMABLE COUNTER DIVIDE
RATIO (RF B COUNTER)
(RF_N[11]-[20])
RF_NB_CNTR
Divide Ratio
9
8
7
6
5
4
3
2
1
0
3
0
0
0
0
0
0
0
0
1
1
4
0
0
0
0
0
0
0
1
0
0
-
-
-
-
-
-
-
-
-
-
-
1,023
1
1
1
1
1
1
1
1
1
1
Note: Divide ratio: 3 to 1023 (Divide ratios less than 3 are prohibited)
RF_NB_CNTR ≥ RF_NA_CNTR + 2
4.2.4 FRACTIONAL MODULUS ACCUMULATOR (FRAC_CNTR)
(RF_N[2]-[5])
Fractional Ratio (F)
FRAC_CNTR
Modulus 15
Modulus 16
RF_N[5]
RF_N[4]
RF_N[3]
RF_N[2]
0
0
0
0
0
0
1/15
1/16
0
0
0
1
2/15
2/16
0
0
1
0
-
-
-
-
-
-
14/15
14/16
1
1
1
0
N/A
15/16
1
1
1
1
4.3 PULSE SWALLOW FUNCTION
fvco = [N + F] x [fosc / R ]
N = (P x B) + A
fosc: Output frequency of the external reference frequency
oscillator
R:
Preset divide ratio of binary 15-bit programmable reference counter (3 to 16383)
P:
Preset modulus of dual modulus prescaler
(LMX2350:RF P=16 or 32, IF P=8)
(LMX2352:RF P=8 or 16, IF P=8)
F:
Fractional ratio (contents of FRAC_CNTR divided by
the fractional modulus)
fvco: Output frequency of external voltage controlled oscillator (VCO)
B:
Preset divide ratio of binary 10-bit programmable
counter
A:
Preset value of binary 4 or 5-bit swallow counter (0 ≤
A ≤ 31 {RF} , 0 ≤ A ≤ 15 {IF} , A+2 ≤ B {RF}, A ≤ B {IF})
4.4 CMOS (Programmable CMOS outputs)
(IF_N[17]-[20])
MSB
FastLock
LSB
TEST
OUT_1
Note: Test bit is reserved and should be set to zero for normal usage.
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16
OUT_0
(Continued)
4.4.1 Programmable CMOS Output Truth Table
BIT
LOCATION
FUNCTION
0
1
OUT_0
IF_N[17]
OUT0 CMOS output pin level
set
LOW
HIGH
OUT_1
IF_N[18]
OUT1 CMOS output pin level
set
LOW
HIGH
FastLock
IF_N[20]
FastLock mode select
CMOS output
FastLock mode
When the FastLock bit is set to one, OUT_0 and OUT_1 are don’t care bits. FastLock mode utilizes the OUT0 and OUT1 output
pins to synchronously switch between active low and TRI-STATE. The OUT0 = LOW state occurs whenever the RF loop’s CP_8X
is selected HIGH while the FastLock bit is set HIGH (see programming description 3.2.2). The OUT0 pin reverts to TRI-STATE
when the CP_8X bit is LOW. Similarly for the IF loop, the synchronous activation of OUT1= LOW or TRI-STATE, is dependent on
whether the CP_GAIN_8 is high or low respectively (see programming description 3.1.4).
4.5 SERIAL DATA INPUT TIMING
DS100831-3
Note: Data shifted into register on clock rising edge. Data is shifted in MSB first.
TEST CONDITIONS: The Serial Data Input Timing is tested using a symmetrical waveform around Vcc/2. The test waveform has an edge rate of 0.6 V/nsec
with amplitudes of 2.2V @ Vcc=2.7 V and 2.6V @ Vcc = 5.5 V.
17
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LMX2350/LMX2352
Programming Description
LMX2350/LMX2352
Programming Description
(Continued)
4.6 LOCK DETECT DIGITAL FILTER
The Lock Detect Digital Filter compares the difference between the phase of the inputs of the phase detector to a RC generated
delay of approximately 15nS. To enter the locked state (Lock = HIGH) the phase error must be less than the 15nS RC delay for
5 consecutive reference cycles. Once in lock (Lock = HIGH), the RC delay is changed to approximately 30nS. To exit the locked
state (Lock = LOW), the phase error must become greater than the 30nS RC delay. When the PLL is in the power down mode,
Lock is forced LOW. A flow chart of the digital filter is shown at right.
DS100831-4
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18
(Continued)
4.7 ANALOG LOCK DETECT FILTER
When the Fo/LD output is configured in analog lock detect mode an external lock detect circuit is needed in order to provide a
steady LOW signal when the PLL is in the locked state. A typical circuit is shown below. The fold output is active low (open drain)
only when analog lock detect mode is selected.
DS100831-5
4.8 TYPICAL LOCK DETECT TIMING
DS100831-6
19
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LMX2350/LMX2352
Programming Description
LMX2350/LMX2352
Physical Dimensions
inches (millimeters) unless otherwise noted
Molded TSSOP, JEDEC Plastic Package (MTC24)
Order Number LMX2350TM or LMX2352TM
NS Package MTC24
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20
inches (millimeters) unless otherwise noted (Continued)
Molded CSP, JEDEC Plastic Package (SLB24A)
Order Number LMX2350SLB or LMX2352SLB
NS Package SLB24A
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LMX2350/LMX2352 PLLatinum Fractional N RF / Integer N IF Dual Low Power Frequency
Synthesizer
Physical Dimensions