How it Works
Datasheet
Loading...
LMX2352SLBX
Datasheet (NSC)
20 pgs407.72 Kb0

Datasheet LMX2352TMX, LMX2352SLBX, LMX2352TM Datasheet (NSC)

Download
Page 1
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
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 (VCO’s).
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.TheLMX2350/
2352 family features very low current consumption; typically LMX2350 (2.5 GHz) 6.75 mA, LMX2352 (1.2 GHz) 5.00 mA at 3.0V.TheLMX2350/2352areavailablein a 24-pin TSSOP surface mount plastic package.
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=5µAtypat3v
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
FastLock™is a trademark of National Semiconductor Corporation. MICROWIRE
™
is a trademark of National Semiconductor Corporation.
PLLatinum
™
is a trademark of National Semiconductor Corporation.
TRI-STATE
®
is a registered trademark of National Semiconductor Corporation.
DS100831-1
PRELIMINARY
June 1999
LMX2350/LMX2352 PLLatinumTM Fractional N RF / Integer N IF Dual Low Power Frequency
Synthesizer
© 1999 National Semiconductor Corporation DS100831 www.national.com
Page 2
Connection Diagram
Pin Descriptions
Pin No.
Pin Name
I/O Description
1 OUT0 O Programmable CMOS output. Level of the output is controlled by IF_N [17] bit. 2 Vcc
RF
- 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.
3V
p
RF
- Power supply for RF charge pump. Must be ≥V
cc
RF
and V
cc
IF
.
4CP
o
RF
O RF charge pump output. Connected to a loop filter for driving the control input of an external
VCO.
5 GND - Ground for RF PLL digital circuitry. 6 fin RF I RF prescaler input. Small signal input from the VCO. 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.
8 GND - Ground for RF PLL analog circuitry. 9 OSCx I/O 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.)
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.)
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.)
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.)
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.)
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.
15 DATA I Binary serial data input. Data entered MSB first. The last two bits are the control bits. High
impedance CMOS input.
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.)
DS100831-2
Order Number LMX2350TM or LMX2352TM
NS Package Number MTC24
www.national.com 2
Page 3
Connection Diagram (Continued)
Pin No.
Pin Name
I/O Description
17 GND - Ground for IF analog circuitry. 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. 19 fin IF I IF prescaler input. Small signal input from the VCO. 20 GND - Ground for IF digital circuitry. 21 CPo
IF
O IF charge pump output. For connection to a loop filter for driving the input of an external VCO.
22 Vp
IF
- Power supply for IF charge pump. Must be ≥ V
cc
RF
and V
cc
IF
.
23 Vcc
IF
- 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.
24 OUT1 O Programmable CMOS output. Level of the output is controlled by IF_N [18] bit.
www.national.com3
Page 4
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 Typ Max Units
Power Supply Voltage Vcc
RF
-0.3 6.5 V
Vcc
IF
-0.3 6.5 V
Vp
RF
-0.3 6.5 V
Vp
IF
-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 +150 C˚ Lead Temperature (Solder 4 sec.) T
L
+260 C˚
ESD - Whole Body Model (Note 2) 2 Kev
Recommended Operating Conditions
Value
Parameter Symbol Min Typ Max Units
Power Supply Voltage Vcc
RF
2.7 5.5 V
Vcc
IF
Vcc
RF
Vcc
RF
V
Vp
RF
Vcc 5.5 V
Vp
IF
Vcc 5.5 V
Operating Temperature TA -40 + 85 C
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.Forguaranteed specifications and test conditions, see the Elec­trical Characteristics. The guaranteed specifications apply only for the test conditions listed.
Note 2: This Device is a high performance RF integrated circuit and is ESD sensitive. Handling and assembly of this device should only be done at ESD­free workstations.
Electrical Characteristics (V
cc
RF
=
V
cc
IF
=
V
P
RF
=
V
P
IF
=
3.0V; −40˚ C
<
T
A
<
85˚ C except as specified)
Sym­bol
Parameter Conditions Min Typ Max Units
General
I
cc
Power Supply Current LMX2350 RF and IF,
V
cc
=
2.7V to 5.5V
6.75 7.75 mA
LMX2352 RF and IF,
V
cc
=
2.7V to 5.5V
5.0 6.0 mA
LMX2350/52 IF only, V
cc
=
2.7V to 5.5V 1.25 1.45 mA
I
CC-PWDN
Power Down Current RF_EN = IF_EN = LOW 5 µA
f
in
RF RF Operating LMX2350 Prescaler = 32 (Note 3) 1.2 2.5 GHz
Frequency Prescaler = 16 (Note 3) 0.5 1.2 GHz
LMX2352 Prescaler = 16 (Note 3) 0.5 1.2 GHz
Prescaler = 8 (Note 3) 0.25 0.5 GHz
f
in
IF IF Operating Frequency 10 550 MHz
f
OSC
Oscillator Frequency No load on OSCx (Note 3) 2 50 MHz
With resonator load on OSCx (Note 3)
2 20 MHz
fφ Phase Detector Frequency RF and IF 10 MHz Pf
in RF
RF Input Sensitivity VCC= 3.0V −15 0 dBm
V
CC
= 5.0V −10 0 dBm
Pf
in IF
IF Input Sensitivity 2.7 V≤VCC≤ 5.5V −10 0 dBm
V
OSC
Oscillator Sensitivity OSCin, OSCx 0.5 V
CC
V
PP
www.national.com 4
Page 5
Electrical Characteristics (V
cc
RF
=
V
cc
IF
=
V
P
RF
=
V
P
IF
=
3.0V; −40˚ C
<
T
A
<
85˚ C except as specified)
(Continued)
Symbol Parameter Conditions Min Typ Max Units Charge Pump
ICPo-
source
RF
RF Charge Pump Output Current (see Programming Description 3.2.2)
VCPo Vp/2, RF_CP_WORD = 0000 −100 µA
ICPo-
sink RF
VCPo = Vp/2, RF_CP_WORD = 0000 100 µA
ICPo-
source
RF
VCPo = Vp/2, RF_CP_WORD = 1111 −1.6 mA
ICPo-
sink RF
VCPo = Vp/2, RF_CP_WORD = 1111 1.6 mA
ICPo-
source
IF
IF Charge Pump Output Current (see Programming Description 3.1.4)
VCPo = Vp/2, CP_GAIN_8 = 0 −100 µA
ICPo-
sink IF
VCPo = Vp/2, CP_GAIN_8 = 0 100 µA
ICPo-
source
IF
VCPo = Vp/2, CP_GAIN_8 = 1 −800 µA
ICPo-
sink IF
VCPo = Vp/2, CP_GAIN_8 = 1 800 µA
ICPo-
Tri
Charge Pump TRI-STATE Current
0.5 ≤ VCPo ≤ Vp - 0.5
-40˚ C
<TA<
85˚ C
-2.5 2.5 nA
ICPo-
sink
vs. ICPo-
source
CP Sink vs. Source Mismatch
VCPo = Vp/2 TA = 25˚ C
RFICPo = 400 µA - 1.6 mA
310
%
ICPo vs. VCPo
CP Current vs. Voltage 0.5 ≤ VCPo ≤ Vp -
0.5 T
A
= 25˚ C
RFICPo = 800 µA - 1.6 mA
815
%
ICPo vs. T CP Current vs
Temperature
VCPo = Vp/2
-40˚ C
<TA<
85˚ C
8
%
Digital Interface
V
IH
High-level Input Voltage (Note 4) 0.8 Vcc V
V
IL
Low-level Input Voltage (Note 4) 0.2 Vcc V
I
IH
High-level Input Current V
IH
=
V
CC
=
5.5 V, (Note 4) −1.0 1.0 µA
I
IL
Low-level Input Current V
IL
=
0, V
CC
=
5.5 V, (Note 4) −1.0 1.0 µA
I
IH
Oscillator Input Current V
IH
=
V
CC
=
5.5 V 100 µA
I
IL
Oscillator Input Current V
IL
=
0, V
CC
=
5.5 V −100 µA
V
OH
High-level Output Voltage
I
OH
=
−500 µA V
CC
−0.4 V
V
OL
High-level Output Voltage
I
OL
=
500 µA 0.4 V
MICROWIRE Timing
t
CS
Data to Clock Setup Time
See Data Input Timing 50 ns
t
CH
Data to Clock Hold Time
See Data Input Timing 10 ns
t
CWH
Clock Pulse Width High See Data Input Timing 50 ns
t
CWL
Clock Pulse Width Low See Data Input Timing 50 ns
t
ES
Clock to Load Enable Set Up Time
See Data Input Timing 50 ns
t
EW
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
www.national.com5
Page 6
Charge Pump Current Specification Definitions
DS100831-7
I1=CP sink current at V
Do
=
Vp − ∆V
I2=CP sink current at V
Do
=
Vp/2
I3=CP sink current at V
Do
=
∆V
I4=CP source current at V
Do
=
Vp − ∆V
I5=CP source current at V
Do
=
Vp/2
I6=CP source current at V
Do
=
∆V
∆V=Voltage offset from positive and negative rails. Dependent on VCO tuning range relative to V
CC
and ground. Typical values are between 0.5V and 1.0V.
Note 5: I
Do
vs V
Do
=
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: I
Do-sink
vs V
Do-source
=
Charge Pump Output Current Sink vs Source Mismatch=[||2| − ||5|]/[
1
⁄
2
*
{||2| + ||5|}]*100
%
Note 7: I
Do
vs T
A
=
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
%
www.national.com 6
Page 7
RF Sensitivity Test Block Diagram
Typical Performance Characteristics
DS100831-8
Note: N=10,000 R=50 P=64 Note: Sensitivity limit is reached when the error of the divided RF output, F
o
LD, is ≥ 1 Hz.
ICCvs V
CC
LMX2350
DS100831-9
ICCvs V
CC
LMX2352
DS100831-10
I
CPO
TRI-STATE vs
CP
O
Voltage
DS100831-11
Charge Pump Current vs CPOVoltage RF_CP_WORD=0000 and 0111 IF CP_GAIN8=0 and 1
DS100831-12
www.national.com7
Page 8
Typical Performance Characteristics (Continued)
Charge Pump Current vs CP
O
Voltage
RF_CP_WORD=0011 and 1111
DS100831-13
Sink vs Source Mismatch (See (Note 6) under Charge Pump Current Specification Definitions)
DS100831-14
RF Input Impedance V
CC
=
2.7V to 5.5V, f
IN
=
50 MHz to
3 GHz (f
IN
Capacitor=100 pF)
DS100831-15
IF Input Impedance V
CC
=
2.7V to 5.5V, f
IN
=
10 MHz to
1 GHz (f
IN
Capacitor=100 pF)
DS100831-16
www.national.com 8
Page 9
Typical Performance Characteristics (Continued)
LMX2350 RF Sensitivity vs Frequency
DS100831-17
LMX2352 RF Sensitivity vs Frequency
DS100831-18
IF Input Sensitivity vs Frequency
DS100831-19
Oscillator Input Sensitivity vs Frequency
DS100831-20
LMX2350 VPVoltage vs VPLoad Current in Vdoubler Mode, T=25˚C
DS100831-21
www.national.com9
Page 10
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.
1.1 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.
1.2 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 ACounter 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.
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.
1.3.2 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
www.national.com 10
Page 11
Functional Description (Continued)
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 100µAor 800µA levels using bit IF_R [19] (see programming description 3.1.4).
1.6 Voltage Doubler
The Vp
RF
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 Vp
RF
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
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 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.
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.
www.national.com11
Page 12
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 10 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 REGISTER BIT LOCATION Last Bit
23 22 212019 18 17 1615141312111098765 4 3 2 10 IF_R OSC FRAC_16 FoLD IF_CP_WORD IF_R_CNTR 0 0 IF_N IF_CTL_WORD CMOS IF_NB_CNTR IF_NA_CNTR 0 1
RF_R DLL_MODE V2_EN RF_CP_WORD RF_R_CNTR 1 0 RF_N RF_CTL_WORD RF_NB_CNTR 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] IF_CP_WORD [1:0] IF_R_CNTR [14:0] 0 0 23 22 21 19 18 17 16 2 1 0
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,theOSCin 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).
www.national.com 12
Page 13
Programming Description (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 109876543210
3 000000000000011 4 000000000000100
- ---------------
32,767 111111111111111
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
0 0 0 IF and RF Analog Lock Detect (Open Drain) 1 0 0 IF Digital Lock Detect 0 1 0 RF Digital Lock Detect 1 1 0 IF and RF Digital Lock Detect 0 0 1 IF R counter 1 0 1 IF N counter 0 1 1 RF R counter 1 1 1 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 LSB DLL_MODE V2_EN RF_CP_WORD [4:0] RF_R_CNTR [14:0] 1 0 23 22 21 17 16 2 1 0
www.national.com13
Page 14
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 0000 200 0001 300 0010 400 0011
- ----
900 1000
- ----
1600 1111
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] CMOS [3:0] IF_NB_CNTR [11:0] IF_NA_CNTR [2:0] 0 1 23 21 20 17 16 5 4 2 1 0
4.1.1 IF_CTL_WORD (IF_R[21]-[23])
MSB LSB IF_CNT_RST PWDN_IF PWDN_MODE
Note: See section 4.2.1.2 for IF control word truth table.
www.national.com 14
Page 15
Programming Description (Continued)
4.1.2 3-BIT IF SWALLOW COUNTER DIVIDE RATIO (IF A COUNTER) (IF_N[2]−[4]) Swallow Count IF_NA_CNTR
(A) 2 1 0
0 000 1 001
- --­7 111
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 109876543210
3 0 0 0000000011 4 0 0 0000000100
- - - ----------
4,095 1 1 1111111111
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] RF_NB_CNTR [9:0] RF_NA_CNTR [4:0] FRAC_CONT [3:0] 1 1 23 21 20 11 10 6 5 2 1 0
4.2.1.1 RF_CTL_WORD (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 Power down mode select Asynchronous power down Synchronous power down PRESC LMX2350 Prescaler Modulus select 16/17
(0.5 to 1.2 GHz operation)
32/33 (1.2 to 2.5 GHz operation)
LMX2352 8/9
(0.25 to 0.5 GHz operation)
16/17 (0.5 to 1.2 GHz operation)
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 pump
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.
www.national.com15
Page 16
Programming Description (Continued)
Synchronous Power down Mode
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.
4.2.2 5-BIT RF SWALLOW COUNTER DIVIDE RATIO (RF A COUNTER) (RF_N[6]-[10])
Swallow Count RF_NA_CNTR
(A) 43210
0 00000 1 00001
- -----
31 11111
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 9876543210
3 0000000011 4 0000000100
- ----------
1,023 1111111111
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 0000 1/15 1/16 0001 2/15 2/16 0010
- - ----
14/15 14/16 1110
N/A 15/16 1111
4.3 PULSE SWALLOW FUNCTION
fvco = [N + F] x [fosc/R]
N=(PxB)+A
F: Fractional ratio (contents of FRAC_CNTR divided by
the fractional modulus)
fvco: Output frequency of external voltage controlled oscil-
lator (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})
fosc: Output frequency of the external reference frequency
oscillator
R: Preset divide ratio of binary 15-bit programmable ref-
erence 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)
4.4 CMOS (Programmable CMOS outputs) (IF_N[17]-[20])
MSB LSB FastLock TEST OUT_1 OUT_0
Note: Test bit is reserved and should be set to zero for normal usage.
www.national.com 16
Page 17
Programming Description (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
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.
DS100831-3
www.national.com17
Page 18
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
www.national.com 18
Page 19
Programming Description (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. Atypical circuit is shown below. The fold output is active low (open drain) only when analog lock detect mode is selected.
4.8 TYPICAL LOCK DETECT TIMING
DS100831-5
DS100831-6
www.national.com19
Page 20
Physical Dimensions inches (millimeters) unless otherwise noted
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
National Semiconductor Corporation
Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com
National Semiconductor Europe
Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80
National Semiconductor Asia Pacific Customer Response Group
Tel: 65-2544466 Fax: 65-2504466 Email: sea.support@nsc.com
National Semiconductor Japan Ltd.
Tel: 81-3-5639-7560 Fax: 81-3-5639-7507
www.national.com
Molded TSSOP, JEDEC Plastic Package (MTC24)
Order Number LMX2350TM or LMX2352TM
NS Package MTC24
LMX2350/LMX2352 PLLatinumTM Fractional N RF / Integer N IF Dual Low Power Frequency
Synthesizer
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
Loading...
Buy Points How it Works FAQ Contact Us Questions and Suggestions Privacy Policy Cookie Policy Terms of Use