TLV5535

8-BIT, 35 MSPS, LOW-POWER ANALOG-TO-DIGITAL CONVERTER

SLAS221 – JUNE 1999

15

POST OFFICE BOX 655303

PRINCIPLE OF OPERATION

ac coupled input (continued)

VIN

AIN

TLV5535

R1

R2

VBIAS

+

–

C1

C2

Figure 14. AC-Coupled Input Circuit

reference terminals

The voltages on terminals REFBI and REFTI determine the TLV5535 input range. Since the device has an

internal voltage reference generator with outputs available on REFBO and REFTO respectively, corresponding

terminals can be directly connected externally to provide a contained ADC solution. Especially at higher

sampling rates, it is advantageous to have a wider analog input range. The wider analog input range is

be derived via a voltage divider from a power supply source. Instead, a bandgap-derived voltage reference

should be used to derive both references via an op amp circuit. Refer to the schematic of the TLV5535 evaluation

module for an example circuit.

When using external references, the full-scale ADC input range and its dc position can be adjusted. The

Table 1 summarizes these limits for 3 cases.

Table 1. Recommended Operating Modes

AVDD

VREFB(min)

VREFB(max)

VREFT(min)

VREFT(max)

(VREFT–VREFB)max

3 V

0.8 V

1.2 V

1.8 V

2.2 V

1 V

3.3 V

0.8 V

1.2 V

2.1 V

2.5 V

1.3 V

3.6 V

0.8 V

1.2 V

2.4 V

2.8 V

1.6 V

digital inputs

The digital inputs are CLK, STDBY, PWDN_REF, and OE. All of these signals, except CLK, have an internal

pulldown resistor to connect to digital ground. This provides a default active operation mode using internal

references when left unconnected.