12 - 6

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12

Serial Control Interface

HMC708LP5 / 708LP5E

v03.0409

0.5 dB LSB 6-BIT DIGITAL

VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz

20

24

28

32

36

40

44

0

4

8

12

16

20

24

28

32

Vdd=3V

Vdd=5V

ATTENUATION STATE (dB)

Pout=-5dBm

Pout=0dBm

Setup limit

-20

-15

-10

-5

0

5

10

15

20

1.5 1.6

1.7 1.8 1.9

2

2.1 2.2 2.3

2.4 2.5

Vdd=3V

Vdd=5V

FREQUENCY (GHz)

S22

S21

S11

the HmC708lp5(e) contains a 3-wire spi compatible digital interface (serin, ClK, le). it is activated when p/s

is kept high. the 6-bit serial word must be loaded msb first. the positive-edge sensitive ClK and le requires

clean transitions. standard logic families work well. if mechanical switches were used, sufficient debouncing should

be provided. When le is high, 6-bit data in the serial input register is transferred to the attenuator. When le is high

ClK is masked to prevent data transition during output loading.

When p/s is low, 3-wire spi interface inputs (serin, ClK, le) are disabled and serial input register is loaded

asynchronously with parallel digital inputs (d0-d5). When le is high, 6-bit parallel data is transferred to the attenuator.

for all modes of operations, attenuation state will stay constant while le is kept low.

[1] see application Circuit [2] maximum gain state with digital attenuator set to minimum attenuation