LMX2326TM National Semiconductor, LMX2326TM Datasheet - Page 10

• Manufacturer Part Number: LMX2326TM
• Manufacturer: National Semiconductor
• Type: PLL Frequency Synthesizerr

Specifications of LMX2326TM

• Number Of Elements: 1
• Supply Current: 7mA
• Pll Input Freq (min): 100MHz
• Pll Input Freq (max): 2.8GHz
• Operating Supply Voltage (typ): 3V
• Operating Temp Range: -40C to 85C
• Package Type: TSSOP
• Operating Supply Voltage (min): 2.3V
• Operating Supply Voltage (max): 5.5V
• Operating Temperature Classification: Industrial
• Pin Count: 16
• Lead Free Status / Rohs Status: Not Compliant

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1.0 Functional Description
1.3.1 Powerdown Operation
Bits F[2] and F[18] provide programmable powerdown modes when the CE pin is HIGH. When CE is LOW, the part is always
immediately disabled regardless of powerdown bit status. Refer to Table 3.
Synchronous and asynchronous powerdown modes are both available by MICROWIRE selection. Synchronous powerdown
occurs if the F[18] bit (Powerdown Mode) is HIGH when F[2] bit (Powerdown) becomes HIGH. Asynchronous powerdown occurs
if the F[18] bit is LOW when its F[2] bit becomes HIGH.
In the synchronous powerdown mode (F[18] = HIGH), the powerdown function is gated by the charge pump to prevent unwanted
frequency jumps. Once the powerdown program bit F[2] is loaded, the part will go into powerdown mode after the first successive
charge pump event.
In the asynchronous powerdown mode (F[18] = LOW), the device powers down immediately after latching LOW data into bit F[2].
The device returns to an actively powered up condition in either synchronous or asynchronous mode immediately upon LE
latching LOW data into bit F[2].
Activation of a powerdown condition in either synchronous or asynchronous mode including CE pin activated powerdown has the
following effects:
1.3.2 Lock Detect Output Characteristics
Output provided to indicate when the VCO frequency is in “lock.” When the loop is locked and the open drain lock detect mode
is selected, the pin’s output is HIGH, with narrow pulses LOW. When digital lock detect is selected, the output will be HIGH when
the absolute phase error is
value of R[19]. Once lock is detected the output stays HIGH unless the absolute phase error exceeds 30 ns for a single reference
cycle. Setting the charge pump to TRI-STATE or power down (bits F2, F18) will reset the digital lock detect to the unlocked state.
The LD precision bit, R[19], will select five consecutive reference cycles, instead of three, for entering the locked state when R[19]
= HIGH.
• Removes all active DC current paths.
• Forces the R, N, and timeout counters to their load state conditions.
• Will TRI-STATE the charge pump.
• Resets the digital lock detect circuitry.
• Debiases the f
• Disables the oscillator input buffer circuitry.
• The MICROWIRE control register remains active and capable of loading the data.
LOW
HIGH
HIGH
HIGH
F[3]
0
0
0
0
1
1
1
1
CE(Pin 10)
IN
F[4]
input to a high impedance state.
0
0
1
1
0
0
1
1
<
15 ns for three or five consecutive phase frequency detector reference cycles, depending on the
F[5]
0
1
0
1
0
1
0
1
TABLE 4. The Fo/LD (pin 14) Output Truth Table
F[2]
X
0
1
1
TABLE 3. Power Down Truth Table
TRI-STATE
R Divider Output (fr)
N Divider Output (fp)
Serial Data Output
Digital Lock Detect (See 1.3.2 LOCK DETECT OUTPUT Section)
n Channel Open Drain Lock Detect (See 1.3.2 LOCK DETECT OUTPUT
Section)
Active HIGH
Active LOW
(Continued)
10
F[18]
X
X
0
1
Fo/LD Output State
Asynchronous Power Down
Normal Operation
Asynchronous Power Down
Synchronous Power Down
Mode