CDCE72010RGCT datasheet(53/73 Pages) TI

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CHARGE PUMP

CDCE72010

www.ti.com.............................................................................................................................................................. SCAS858A – JUNE 2008 – REVISED JULY 2009

The Charge Pump drives the loop filter that controls the external VCO/VCXO. The Charge pump frequency is

determined by the PFD frequency since the function of the charge pump is to translate the UP DOWN signals of

the PFD into current pulses that drives the external filter. The Charge pump current is set by the control vector

ICP [3:0]. The error amplifier operates from 0.7V to the VDD supply voltage. See the table below for ICP settings.

Table 13. CP, Charge Pump Current (Register 0 RAM Bits [17:14])

TYPICAL CHARGE PUMP

ICP3

ICP2

ICP1

ICP0

CURRENT

µA (3-State)

200

µA

400

µA

600

µA

800

µA

1.0 mA

1.2 mA

1.4 mA

1.6 mA

1.8 mA

2.0 mA

2.2 mA(1)

2.4 mA

2.6 mA

2.8 mA

3.0 mA

(1)

Default

The ‘Preset Charge-Pump to VCC_CP/2 is a useful feature to quickly set the center frequency of the VC(X)O after

Power-up or Reset. The adequate control voltage for the VC(X)O will be provided to the Charge-Pump output by

an internal voltage divider of 1K

Ω/1KΩ to VCC_CP and GND (VCC_CP/2).

This feature helps to get the initial frequency accuracy, i.e. required at CPRI (Common Public Radio Interface) or

OBSAI (Open Base Station Architecture Initiative).

The Preset Charge-Pump to VCC_CP/2 can be set and reset by SPI register.

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