ML2712CH 查看數據表（PDF） - Micro Linear Corporation

零件编号

产品描述 (功能)

生产厂家

ML2712CH

2.4GHz RF Transceiver

Micro Linear Corporation 

PRELIMINARY

ML2712

CONTROL INTERFACES (CONTINUED)

CONTROL WORD C

2LO ND & NS counters are denoted as ND2 & NS2.

The binary weighted modulus values are loaded

using CONTROL WORD C as shown in Table 13. The

prescaler used in the 2LO PLL is a 14/15 dual modulus

type giving the 2LO frequency in MHz as f2LO = (14 ´

ND2 + NS2) ´ (fREF /M).

The reference divider ratio M is also set in CONTROL

WORD C (Table 4)

Control Bit

CONTROL WORD C

b9

b10

0

0

0

0

0

1

0

1

Reference Division Ratio M

b11

0

16

1

32 (Power up Default)

0

20

1

40

Table 13. Reference Division Ratio

CONTROL WORD D

The 1LO PLL is a dual modulus type as described

above. 1LO ND & NS counters are denoted in

ML2712 as ND1 & NS1. Modulus values are binary

weighted and are loaded using CONTROL WORD D as

shown in Table 4. The prescaler used in the 1LO PLL

is a 40/41 dual modulus type giving the 1LO

frequency in MHz as

f1LO = (40 ´ ND1 + NS1) ´ (fREF /M).

CONTROL WORD E

The 8-bit DAC and Comparator form a tracking

Analog-to-Digital converter (ADC) intended to

connect to the RSSI (Receive Signal Strength

Indicator) on the ML2713.

The tracking ADC is represented in Figure 10.

CONTROL WORD E is used to program a voltage into

the 8-bit DAC setting up a voltage on the inverting

terminal of the Comparator. If the RSSI voltage

exceeds that on the DAC then RSSITH signals logic

high.

Typically, a baseband IC will be used to program RSSI

values into the ML2712 corresponding to a known

receive signal level. The RSTH value (high/low) is

sensed by the baseband IC to determine if the signal

strength threshold has been exceeded. By

successively programming the 8-bit DAC using CONTROL

WORD E the baseband IC can measure the RSSI voltage

closely.

January, 2000

RSSI INPUT

VOLTAGE

TPL

OUTPUT

VOLTAGE

+

RSTH

–

BASEBAND

IC

8

SCALING

AMPLIFIER

8 BIT D/A

CONTROL

WORD D

[B4...B11]

Figure 10. Charge Pump Polarity

Alternatively, the DAC may be programmed with a

threshold value that when exceeded triggers the baseband

IC into receive mode. In this mode the DAC and

Comparator are used to provide the necessary circuits for

Clear Channel Assessment (CCA) as defined in IEEE

802.11. Figure 11 shows the relationship between RSSI

DAC code (in decimal) programmed into ML2712 via

CONTROL WORD E and the DAC RSSI voltage threshold.

250

200

VCCD = 5.0V

VCCA = 3.3V

150

100

50

0

1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3

RSSI THRESHOLD VOLTAGE (V)

Figure 11. Parallel Control Over-Ride Using LBC Bit

The DAC also has a general purpose use. The DAC voltage

programmed using CONTROL WORD E is fed to scaling

circuit before appearing externally at TPL. While the DAC

output is suitable for general use, a likely use for the

voltage is for transmit power control. In this mode of

operation the DAC voltage corresponding to the required

transmitter output power can be programmed before

transmit operation. The relationship between TPL voltage

versus DAC programming is shown in Figure 12.

250

VCCD = 5.0V

VCCA = 3.3V

200

LOAD ON TPL = 1MΩ

IN PARALLEL WITH 15pF

150

100

50

0

0.5

1.0

1.5

2

2.5

3

TPL VOLTAGE (V)

Figure 12. Control of ML2712 DAC Comparator

PRELIMINARY DATASHEET

17

Share Link: