2.3.7 Power Down Mode Table

Main PLL

Auxiliary PLL

Main

Counters

Auxiliary

Counters

OSC

Active

Active

ON

ON

ON

Active

Powered Down

ON

OFF

ON

Powered Down

Active

OFF

ON

ON

Powered Down

Powered Down

OFF

OFF

OFF

2.4 PROGRAMMABLE MODES

Several modes of operation can be programmed with bits R15–R19 including the phase detector polarity, charge pump magni-

tude, charge pump TRI-STATE and the output of the Fo/LD pin. The programmable modes are shown in Table 1. Truth table for

the programmable modes and Fo/LD output are shown in Table 2 and Table 3.

2.4.1 Programmable Modes Table

R19

R18

R17

R16

R15

Address[1:0]

f

Charge

Pump

TRI-STATE

Charge

Pump

Magnitude

Phase

Detector

Polarity

FoLD 1

FoLD 0

Aux_CP

Aux_CP

Aux_PD_POL

0 0

FoLD 3

FoLD 2

Main_CP

Main_CP

Main_PD_POL

1 0

2.4.2 Mode Select Truth Table

CP

CP

PD_POL (Note 8)

0

Normal Operation

1X Current

LOW

1

TRI-STATE

4X Current

HIGH

Note 6: Both synchronous and asynchronous power down modes are available with the LMX237X family to be able to adapt to different types of applications. The

MICROWIRE control register remains active and capable of loading and latching in data during all of the powerdown modes.

Note 8: See Section 2.4.3

2.4.3 Phase Detector Polarity (Aux_PD_POL, Main_PD_POL)

Depending upon VCO characteristics, the Aux_PD_POL

(Aux_R15) and Main_PD_POL (Main_R15) bits should be

set accordingly:

When VCO characteristics are positive like (1), R15 should

be set HIGH;

When VCO characteristics are negative like (2), R15 should

be set LOW.

VCO CHARACTERISTICS

DS101026-5

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