LMX2364 National Semiconductor Corporation, LMX2364 Datasheet - Page 21

• Manufacturer Part Number: LMX2364
• Description: 2.6 Ghz Pllatinum Fractional Rf Frequency Synthesizer With 850 Mhz Integer If Frequency Synthesizer
• Manufacturer: National Semiconductor Corporation

Charge Pump Currents
The above block diagram shows the test procedure for test-
ing the RF and IF charge pumps. These tests include abso-
lute current level, mismatch, and leakage. In order to mea-
sure the charge pump currents, a signal is applied to the high
frequency input pins. The reason for this is to guarantee 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 OSCinIF Pin is tied
to the supply. The charge pump currents can be measured
by simply programming the phase detector to the necessary
polarity. For instance, in order to measure the RF charge
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pump current, a 10 MHz signal is applied to the FinRF pin.
The source current 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 and IF PLL charge
pump currents are also controlled by the RF_CP and IF_CP
bits. Once the charge pump currents are known, the mis-
match can be calculated as well. In order to measure leak-
age currents, the charge pump current is set to a TRI-STATE
mode by enabling the counter reset bits. This is RF_RST for
the RF PLL and IF_RST for the IF PLL.
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