LTC2640 datasheet(14/24 Pages) LINER

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LTC2640

2640fb

TYPICAL PERFORMANCE CHARACTERISTICS

LTC2640

Multiplying Bandwidth

Noise Voltage vs Frequency

0.1Hz to 10Hz Voltage Noise

PIN FUNCTIONS

CS/LD (Pin 1): Serial Interface Chip Select/Load Input.

When CS/LD is low, SCK is enabled for shifting data on

SDI into the register. When CS/LD is taken high, SCK

is disabled and the speciﬁed command (see Table 1) is

executed.

SCK (Pin 2): Serial Interface Clock Input. CMOS and TTL

compatible.

SDI (Pin 3): Serial Interface Data Input. Data on SDI is

clocked into the DAC on the rising edge of SCK. The LTC2640

accepts input word lengths of either 24- or 32-bits.

GND (Pin 4): Ground.

VCC (Pin 5): Supply Voltage Input. 2.7V ≤ VCC ≤ 5.5V

(LTC2640-L) or 4.5V ≤ VCC ≤ 5.5V (LTC2640-H). Bypass

to GND with a 0.1μF capacitor.

REF (Pin 6): Reference Voltage Input or Output. When

External Reference mode is selected, REF is an input

(0V ≤ VREF ≤ VCC) where the voltage supplied sets the

full-scale voltage. When Internal Reference is selected,

the 10ppm/°C 1.25V (LTC2640-L) or 2.048V (LTC2640-H)

internal reference is available at the pin. This output may

be bypassed to GND with up to 10μF (0.33μF is recom-

mended), and must be buffered when driving external DC

load current.

VOUT (Pin 7): DAC Analog Voltage Output.

CLR (Pin 8, LTC2640-Z): Asynchronous Clear Input. A

logic low at this level-triggered input clears all registers

and causes the DAC voltage output to reset to Zero. CMOS

and TTL compatible.

REF_SEL (Pin 8, LTC2640-M): Selects default Reference

at power-up. Tie to VCC to select the Internal Reference,

or GND to select an External Reference. After power-up,

the logic state at this pin is ignored and the reference may

be changed only by software command.

FREQUENCY (Hz)

100

200

300

2640 G34

100

10k

100k

500

400

INTERNAL REF.

CODE = MIDSCALE

LTC2640-H

(VCC = 5V)

LTC2640-L

(VCC = 4V)

1s/DIV

10μV/DIV

2640 G35

LTC2640-L, VCC = 4V

INTERNAL REF.

CODE = MIDSCALE

FREQUENCY (Hz)

–2

–6

–8

–14

–4

–12

–10

–16

–18

100k

2640 G33

1000k

10k

VCC = 5V

VREF(DC) = 2V

VREF(AC) = 0.2VP-P

CODE = FULL SCALE

TA = 25°C, unless otherwise noted.

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