Application Section

Pin Description

See

Figure 1 for the basics of a typical LMV248 dual band

application.

See

Figure 2 for a simplified block diagram of the LMV248’s

internal architecture

TABLE 1.

Pin

Name

Description

Power Supply

5, 6

GND

Power Ground; both pins must be tied together.

9,11, 13

V

DD

Positive Supply Voltage

Digital Inputs

1

BS

Selects the RF detector input (VfA or VfB) and the corresponding output

amplifier (Out_A or Out_B) enabled when the Tx_En is HIGH. The

compensation is also connected to the correct amplifier automatically.

A HIGH input enables Out_A.

A LOW input enables Out_B.

The other unselected output is held close to GND.

2

Tx_En

A HIGH input enables the input and output amplifiers (VfA and Out_A or

VfB and Out_B) selected by the band select pin, BS.

Analog Inputs

10

VfA

Detector diodes for the RF power detector are connected here. An

internal switch connects a 10µA current sink to the input pin selected by

BS to bias the detector diode. This signal is referenced to V

Notes 9 and 11).

12

VfB

14

TC

The reference diode used for temperature compensation of the VfA and

VfB RF power signals is connected here. Internally, a 10µA current sink

connects to this pin to bias the reference diode. This signal is referenced

to V

15

Ramp

Sets the RF output power level. The useful input voltage range is from

0.2V to 1.8V, although voltages from 0V to V

filter with a corner frequency of approximately 1.6MHz smooths the

Ramp signal, to eliminate step discontinuities from the baseband DAC’s

output.

16

V

HOME

Sets the desired minimum output voltage of the controller (selected by

BS) to the threshold voltage of the RF power amplifier. This reduces

ramp up time, since a smaller voltage range is slewed across. The

recommended input voltage range is from 0V to 2V.

Compensation

7

Comp1

Connect an external RC network here for overall loop compensation and

to control the closed loop frequency response. In most cases this

network will be simply a capacitor. Conventional loop stability techniques

can be used in selecting this network, such as Bode plots.

8

Comp2

Outputs

4

Out A

A rail-to-rail output capable of sourcing is 6mA, sinking 2mA, with less

than 200mV drop including over temperature. The output is free from

glitches when enabled by Tx_En. When an output is not selected by BS,

it is close to GND. When Tx_En is low, output voltages are near GND.

3

Out B

Note 10: For the digital inputs, a LOW is

≤ 0.8V and HIGH is ≥ 1.8V.

Note 11: RF power detection is usually via a RF detector diode and a RF power coupler.

www.national.com

6