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LTC1606AI

16-Bit, 250ksps, Single Supply ADC

Linear Technology 

LTC1606

APPLICATIO S I FOR ATIO

capacitor as close to the device input pin as possible. If an

amplifier is to be used to drive the input, care should be

taken to select an amplifier with adequate accuracy, linear-

ity and noise for the application. The following list is a

summary of the op amps that are suitable for driving the

LTC1606. More detailed information is available in the

Linear Technology data books and LinearViewTM CD-ROM.

LT1007: Low noise precision amplifier. 2.7mA supply

current ±5V to ±15V supplies. Gain bandwidth product

8MHz. DC applications.

LT1097: Low cost, low power precision amplifier. 300µA

supply current. ±5V to ±15V supplies. Gain bandwidth

product 0.7MHz. DC applications.

LT1227: 140MHz video current feedback amplifier. 10mA

supply current. ±5V to ±15V supplies. Low noise and low

distortion.

LT1360: 37MHz voltage feedback amplifier. 3.8mA supply

current. ±5V to ±15V supplies. Good AC/DC specs.

LT1363: 50MHz voltage feedback amplifier. 6.3mA supply

current. Good AC/DC specs.

LT1364/LT1365: Dual and quad 50MHz voltage feedback

amplifiers. 6.3mA supply current per amplifier. Good AC/

DC specs.

LT1468: 90MHz 22V/µs 16-bit accurate amplifier.

LT1469: Dual LT1468

Internal Voltage Reference

The LTC1606 has an on-chip, temperature compensated,

curvature corrected, bandgap reference, which is factory

trimmed to 2.50V. The full-scale range of the ADC is equal

to (±4 • VREF) or nominally ±10V. The output of the

reference is connected to the input of a buffer (1.64x)

through a 4k resistor (see Figure 3). The input to the buffer

or the output of the reference is available at REF (Pin 3).

The internal reference can be overdriven with an external

reference if more accuracy is needed. The buffer output

drives the internal DAC and is available at CAP (Pin 4). The

CAP pin can be used to drive a steady DC load of less than

2mA. Driving an AC load is not recommended because it

can cause the performance of the converter to degrade.

LinearView is a trademark of Linear Technology Corporation

REF

3

(2.5V)

2.2µF

+

CAP

4

(4.096V)

10µF

4k

–

BANDGAP

REFERENCE

R

0.64R

INTERNAL

CAPACITOR

DAC

1606 • F03

Figure 3. Internal or External Reference Source

For minimum code transition noise, the REF pin and the

CAP pin should each be decoupled with a capacitor to

filter wideband noise from the reference and the buffer

(2.2µF tantalum for the REF pin and 10µF tantalum for the

CAP pin). To prevent the 10µF bypass capacitor from

discharging through the CAP pin if the positive supply

(VDIG and VANA) were to drop, a diode (1N4148 or

equivalent) can be placed between the CAP pin and the

positive supply.

Offset and Gain Adjustments

The LTC1606 offset and full-scale errors have been trimmed

at the factory with the external resistors shown in Figure

4. This allows for external adjustment of offset and full

scale in applications where absolute accuracy is impor-

tant. See Figure 5 for the offset and gain trim circuit. The

100k resistor in parallel with the 33.2k is only needed for

externally trimming the offset. First, adjust the offset to

zero by adjusting resistor R3. Apply an input voltage

of –152.6µV (– 0.5LSB) and adjust R3 so the code is

±10V INPUT

200Ω

1%

4.096V +

33.2k

1%

10µF

1

2

VIN

AGND1

2.2µF

LTC1606

3 REF

4

CAP

5

AGND2

1606 • F04

Figure 4. ±10V Input Without Trim

1606fa

9

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