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REFERENCE CIRCUIT

29

30

31

R EF P

R EF M

IR EF

1 W

1 W

56.2 kW

1 mF

1 mF

CLOCK INPUT

5 kW

5 kW

3 pF

3 pF

6 pF

CLKP

CLKM

CM

CM

ADS5510

SLAS499 – JANUARY 2007

The ADS5510 has built-in internal reference generation, requiring no external circuitry on the printed circuit

board (PCB). For optimum performance, it is best to connect both REFP and REFM to ground with a 1-

µF

decoupling capacitor (the 1-

Ω resistor shown in Figure 29 is optional). In addition, an external 56.2-kΩ resistor

should be connected from IREF (pin 31) to AGND to set the proper current for the operation of the ADC, as

shown in Figure 29. No capacitor should be connected between pin 31 and ground; only the 56.2-k

Ω resistor

should be used.

Figure 29. REFP, REFM, and IREF Connections for Optimum Performance

The ADS5510 clock input can be driven with either a differential clock signal or a single-ended clock input, with

little or no difference in performance between both configurations. The common-mode voltage of the clock inputs

is set internally to CM (pin 17) using internal 5-k

Ω resistors that connect CLKP (pin 10) and CLKM (pin 11) to

CM (pin 17), as shown in Figure 30.

Figure 30. Clock Inputs

When driven with a single-ended CMOS clock input, it is best to connect CLKM (pin 11) to ground with a

0.01-

µF capacitor, while CLKP is ac-coupled with a 0.01-µF capacitor to the clock source, as shown in

Figure 31.

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