ADA4350ARUZ-R7 datasheet(29/38 Pages) AD

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ADA4350

Data Sheet

Rev. B | Page 28 of 37

APPLICATIONS INFORMATION

CONFIGURING THE ADA4350

See the EVAL-ADA4350RUZ-P user guide for details on the

basic configuration of the ADA4350, and how to use the

evaluation board. For more details on configuring the ADC

driver in a different gain setting, see the ADA4941-1 data sheet.

The gain settings of the ADA4350 can be chosen via the SPI

interface or manually through a 5-lead DIP switch.

SELECTING THE TRANSIMPEDANCE GAIN PATHS

MANUALLY OR THROUGH THE PARALLEL

INTERFACE

In the manual mode (or parallel mode), only five out of the six

transimpedance paths can be accessed (FB0 to FB4). Figure 55

shows the simplified schematics of the ADA4350 and the positions

of FB0 to FB4. In this example, the first two feedback paths

(FB0 and FB1) are configured as two different transimpedance

gain paths.

To operate in manual mode or in parallel mode, set the EN pin

(Pin 16) and the MODE pin (Pin 17) to Logic 1. In this mode,

Pin 19 to Pin 23 represent P0 through P4, respectively. To select

one gain, set the corresponding Px pin to Logic 1, and set all

other Px pins to Logic 0. Table 13 shows the relationship between

the gain select switches (P0 through P4) and the gain path

selected.

Setting more than one Px pin to Logic 1 results in connecting

the selected gain paths in parallel.

Table 13. Manual Mode or Parallel Mode Operation

Bit On

Switch Closed

Gain Path Selected

S0 and S6

FB0

S1 and S7

FB1

S2 and S8

FB2

S3 and S9

FB3

S4 and S10

FB4

SELECTING THE TRANSIMPEDANCE GAIN PATHS

THROUGH THE SPI INTERFACE (SERIAL MODE)

For serial mode operation, set the EN pin (Pin 16) to Logic 1

and the MODE pin (Pin 17) to Logic 0. In serial mode, Pin 19

is LATCH, Pin 20 is SCLK, Pin 21 is SDO, Pin 22 is SDI, and Pin 23

is CS. Serial mode operation uses a 24-bit command to configure

each individual switch, S0 through S11, as well as additional

options. Table 14 shows the 24-bit map used in serial mode

operation. Table 15 shows the example codes that select the

various transimpedance gain paths.

Multifunction pin names may be referenced by their relevant

function only.

VOUT2

ADC DRIVER

SWITCHING NETWORK

FET AMP

IN-P

VOUT1

SPI INTERFACE

IN-N

ADA4350

S10

S11

RF0

CF0

RF1

CF1

Figure 55. Simplified Schematic

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