LTC6226/LTC6227

20

Rev 0

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TYPICAL APPLICATIONS

Figure 6. Single-Ended to Differential Driver for 16-Bit ADC

Figure 7. Measured Performance of the LTC6227 Based Single-Ended to Differential Converter Driving the LTC2323-16 ADC

–

+

200pF

62267 F06

TO CONTROL

LOGIC

(FPGA, CPLD,

DSP, ETC.)

1/2 LTC6227

LTC2323-16

REFOUT1

VBYP1

SDO1

CLKOUT

SCK

–

+

1/2 LTC6227

50

5.5V

50

310

310

4.096V

0V

–5.5V

2.048V

200pF

10µF

10µF

SNR = 81 dB

SFDR = 84.35 dB

FREQUENCY (kHz)

0

500

1000

1500

2000

2500

–180

–160

–140

–120

–100

–80

–60

–40

–20

0

62267 F07

High Speed Low Voltage Low Noise Instrumentation

Amplifier with High CMRR

Figure 8 shows a three op amp instrumentation ampli-

fier with a gain of 10V/V which can operate on a wide

range of supply voltages. The resistors are implemented

using instances of the LT5401, a matched resistor array

chip. The resistor matching of U3 is crucial in achieving

high common mode rejection. The front end gain stage

resistors were also implemented using instances of the

LT5401, but can be implemented using other means

as well, since they are not crucial for common mode

rejection. Implementing them using the LT5401 minimizes

gain variation across temperature. The amplifiers were

implemented using instances of the LTC6227MS8, and

supply voltages of ±1.5V were used. Figure 9 shows the

measured frequency response, and Figure 10 shows the

measured CMRR of the instrumentation amplifier, with the

single ended output observed. Figure 11 shows the tran-

offset and 1/f noise allow for wide band operation down

to DC. The broadband input referred noise of 4.6nV/√Hz

is dominated by the resistors.