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MAX2402EAP

800MHz to 1000MHz Transmitter

Maxim Integrated 

800MHz to 1000MHz Transmitter

BADJ can be left open or adjusted with a single pull-

up or pull-down resistor to VCC or GND, respectively.

The value of this resistor determines the amount of

adjustment applied. A single resistor results in no cur-

rent flow at BADJ during power-down (whereas a

resistor divider always has current flowing through the

resistors). Table 1 shows the approximate bias adjust

voltage at the pin for different resistor values. At lower

LO frequencies, where the transmitter gain and output

power is the highest, setting BADJ to a low voltage

(maximum bias current) causes excessive current in

the output and can cause unstable behavior in the IC.

At lower LO frequencies (around 800MHz), more than

22dBm of power is easily obtained with BADJ set for

3V or more. If higher bias current and less distortion is

desired in the 800MHz range, using a lower inductor

value on LGND (pin 11) (see the Typical Application

Circuit) might make the desired bias level stable. At

higher frequencies (near 1000MHz), a lower bias level

voltage results in more power (see the Output Power vs.

Bias Control Voltage vs. Frequency graph in the Typical

Operating Characteristics).

Power Amplifier Output

The power amplifier has an open-collector output that

can drive into a load of 30Ω to 50Ω; however, maximum

power transfer is obtained at about 35Ω. 27nH to

ground is recommended on LGND (pin 11), as shown

in the Typical Application Circuit. This inductor is used

as a current source on the base of the output stage to

pull stored charge out of the base.

SHDN Input

The SHDN input completely shuts down the current

from the supply and all signal pins when switched

below 0.5V. During normal operation, SHDN should

remain above VCC - 0.5V.

The shutdown control shuts down the total current to

below 150nA (typ). Power-up occurs within 10µs.

__________Applications Information

The MAX2402 transmitter operates within the 800MHz

to 1000MHz frequency range. Figure 1 shows a typical

application circuit. Additional applications information

can be obtained from the MAX2402 evaluation kit

manual.

Table 1. Bias-Adjust Voltage for Various

Resistor Values

Resistor BADJ with Resistor BADJ with Resistor

Value (Ω) Connected to GND (V)* Connected to VCC (V)

10k

0.36

4.54

20k

0.63

4.27

30k

0.84

4.05

40k

1.00

3.89

50k

1.13

3.75

100k

1.54

3.34

200k

1.89

3.00

300k

2.05

2.85

400k

2.13

2.75

500k

2.20

2.68

1M

2.31

2.57

* Typical variation of BADJ over temperature and process is

less than 5%.

VARIABLE

GAIN CONTROL

MODULATION

VCC

39pF

1

VGC

2

MOD

3

GND

4

VCC

20

GND

19

VCC

18

GND

17

GND

VCC

39pF 0.01µF

5

MAX2402

16

GND

OUT

50Ω

6

LO+

VCO

7 LO-

15

GND

OUT 14

VCC

47nH

50Ω

8

13

GND

GND

39pF

VCC

SHUTDOWN

CONTROL

9

SHDN

12

VCC

10

BADJ

11

LGND

300k

27nH

Figure 1. Typical Application Circuit

_______________________________________________________________________________________ 5

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