LMX2485E EVAL National Semiconductor, LMX2485E EVAL Datasheet - Page 16

• Manufacturer Part Number: LMX2485E EVAL
• Description: BOARD EVALUATION LMX2485E
• Manufacturer: National Semiconductor
• Series: PLLatinum™r

Specifications of LMX2485E EVAL

• Main Purpose: Timing, Frequency Synthesizer
• Utilized Ic / Part: LMX2485E
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -

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Bench Test Setups
Charge Pump Current Measurement Procedure
The above block diagram shows the test procedure for testing
the RF and IF charge pumps. These tests include absolute
current level, mismatch, and leakage measurement. In order
to measure the charge pump currents, a signal is applied to
the high frequency input pins. The reason for this is to guar-
antee that the phase detector gets enough transitions in order
to be able to change states. If no signal is applied, it is possible
that the charge pump current reading will be low due to the
fact that the duty cycle is not 100%. The OSCin Pin is tied to
the supply. The charge pump currents can be measured by
simply programming the phase detector to the necessary po-
larity. For instance, in order to measure the RF charge pump,
RF TRI-STATE
IF TRI-STATE
Current Test
RF Source
IF Source
RF Sink
IF Sink
RF_CPG
0 to 15
0 to 15
X
X
X
X
RF_CPP
0
1
X
X
X
X
16
a 10 MHz signal is applied to the FinRF pin. The source cur-
rent can be measured by setting the RF PLL phase detector
to a positive polarity, and the sink current can be measured
by setting the phase detector to a negative polarity. The IF
PLL currents can be measured in a similar way. Note that the
magnitude of the RF PLL charge pump current is controlled
by the RF_CPG bit. Once the charge pump currents are
known, the mismatch can be calculated as well. In order to
measure leakage, the charge pump is set to a TRI-STATE
mode by enabling the RF_CPT and IF_CPT bits. The table
below shows a summary of the various charge pump tests.
RF_CPT
0
0
1
X
X
X
IF_CPP
X
X
X
0
1
X
IF_CPT
20087769
X
X
X
0
0
1