ML13175/ML13176

LANSDALE Semiconductor, Inc.

PIN FUNCTION DESCRIPTIONS

Pin

Symbol

Internal Equivalent

Circuit

Description/External

Circuit Requirements

8

Xtale

VCC

9

Xtalb

12k

8.0k

Crystal Oscillator Inputs

The internal reference oscillator is configured as a common

emitter Colpitts. It may be operated with either a fundamental

or overtone crystal depending on the carrier frequency and the

internal prescaler. Crystal oscillator circuits and specifications

of crystals are discussed in detail in the applications section.

9

Xtalb

Xtale

8

9

4.0k

With VCC = 3.0 Vdc, the voltage at Pin 8 is approximately 1.8

Vdc and at Pin 9 is approximately 2.3 Vdc. 500 to 1000 mVp–p

should be present at Pin 9. The Colpitts is biased at 200

µA;

additional drive may be acquired by increasing the bias to

approximately 500

µA. Use 6.2 k from Pin 8 to ground.

10

Reg. Gnd

VCC

5.0p

Reg

Regulator Ground

An additional ground pin is provided to enhance the stability of

the system. Decoupling to the VCC (RF ground) is essential; it

should be done at the ground return for Pin 10.

11

Enable

Reg. Gnd

10

Subcon

Enable

11

p

8.0k

2.4k

Device Enable

The potential at Pin 11 is approximately 1.25 Vdc. When Pin 11

is open, the transmitter is disabled in a power down mode and

draws less than 1.0

µA ICC if the MOD at Pin 16 is also open

(i.e., it has no current driving it). To enable the transmitter a

current source of 10

µA to 90 µA is provided. Figures 3 and 4

show the relationship between ICC, VCC and Ireg. enable. Note

that ICC is flat at approximately 10 mA for Ireg. enable = 5.0 to

100

µA (Imod = 0).

12

VCC

VCC

VCC

12

Supply Voltage (VCC)

The operating supply voltage range is from 1.8 Vdc to 5.0 Vdc.

In the PCB layout, the VCC trace must be kept as wide as

possible to minimize inductive reactances along the trace; it is

best to have it completely fill around the surface mount

components and traces on the circuit side of the PCB.

13 & 14

Out 1 and

Out 2

VCC

16

14

13

Differential Output

The output is configured differentially to easily drive a loop

antenna. By using a transformer or balun, as shown in the

application schematic, the device may then drive an unbalanced

low impedance load. Figure 6 shows how much the Output

Power and Free–Running Oscillator Frequency change with

temperature at 3.0 Vdc; Imod = 2.0 mA.

15

Out_Gnd

Imod

Out 2

Out 1

16

14

13

Output Ground

This additional ground pin provides direct access for the output

ground to the circuit board VEE.

16

Imod

Out_Gnd

15

AM Modulation/Power Output Level

The DC voltage at this pin is 0.8 Vdc with the current source

active. An external resistor is chosen to provide a source

current of 1.0 to 3.0 mA, depending on the desired output power

level at a given VCC. Figure 23 shows the relationship of Power

Output to Modulation Current, Imod. At VCC = 3.0 Vdc, 3.5 dBm

power output can be acquired with about 35 mA ICC.

For FM modulation, Pin 16 is used to set the desired output

power level as described above.

For AM modulation, the modulation signal must ride on a

positive DC bias offset which sets a static (modulation off)

modulation current. External circuitry for various schemes is

further discussed in the Applications Information section.

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Issue c