ADC10064CIWM datasheet(8/14 Pages) NSC

8 / 14 page

Timing Diagrams

Functional Description

The ADC10061, ADC10062 and ADC10064 digitize an ana-

log input signal to 10 bits accuracy by performing two

lower-resolution “flash” conversions. The first flash conver-

sion provides the six most significant bits (MSBs) of data,

and the second flash conversion provides the four least sig-

nificant bits LSBs).

Figure 3 is a simplified block diagram of the converter. Near

the center of the diagram is a string of resistors. At the bot-

tom of the string of resistors are 16 resistors, each of which

has a value 1/1024 the resistance of the whole resistor

string. These lower 16 resistors (the LSB Ladder ) therefore

have a voltage drop of 16/1024, or 1/64 of the total reference

voltage (V

REF+ −VREF−) across them. The remainder of the

resistor string is made up of eight groups of eight resistors

connected in series. These comprise the MSB Ladder. Each

section of the MSB Ladder has 1⁄8 of the total reference volt-

age across it, and each of the LSB resistors has 1/64 of the

DS011020-9

FIGURE 1. Mode 1. The conversion time (t

CONV) is set by the internal timer.

DS011020-10

FIGURE 2. Mode 2 (RD Mode). The conversion time (t

CRD) includes the

sampling time and is determined by the internal timer.

ADC10064CIWM Datasheet(PDF) 8 Page - National Semiconductor (TI)