LT1012 datasheet(9/24 Pages) LINER

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LTC2758

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pin FuncTions

S2 (Pin 25): Span Bit 2 Input. In Manual Span mode (M-

SPAN tied to VDD), Pins S0, S1 and S2 are pin-strapped to

select a single fixed output range for all DACs. These pins

shouldbetiedtoeitherGNDorVDDeveniftheyareunused.

LDAC (Pin 26): Asynchronous DAC Load Input. When

LDAC is a logic low, all DACs are updated (CS/LD must

be high).

IOUT2BF, IOUT2BS (Pins 28, 29): DAC B Current Output

Complement Force and Sense Pins. Tie to ground via a

clean, low-impedance path. These pins may be used with

a precision ground buffer amp as a Kelvin sensing pair

(see the Applications Information section).

RINB (Pins 31, 32): Input Resistor for the DAC B External

Reference Inverting Amplifier. The 20k input resistor is

connected internally from RINB to RCOMB. For normal op-

eration tie RINB to the external positive reference voltage

(seeTypicalApplication).Eitherorbothoftheseprecision-

matched resistor sets (each set comprising RINX, RCOMX

and REFX) may be used to invert positive references to

provide the negative voltages needed by the DACs. Typi-

cally 5V; accepts up to ±15V. Pins 31 and 32 are internally

shorted together.

GEADJB (Pin 33): Gain Adjust Pin for DAC B. This control

pin can be used to null gain error or to compensate for

reference errors. The gain change expressed in LSB is

the same for any output range. See System Offset and

Gain Adjustments in the Operation section. Tie to ground

if not used.

RCOMB (Pin 34): Virtual Ground Point for the DAC B Ref-

erence Amplifier Inverting Resistors. The 20k reference

inverting resistors are connected internally from RINB to

RCOMB and from RCOMB to REFB, respectively (see Block

Diagram). For normal operation tie RCOMB to the negative

input of the external reference inverting amplifier (see

Typical Application).

REFB (Pins 35, 36): Feedback Resistor for the DAC B

Reference Inverting Amplifier, and Reference Input for

DAC B. The 20k feedback resistor is connected internally

from REFB to RCOMB. For normal operation tie this pin to

the output of the DAC B reference inverting amplifier (see

Typical Application). Typically –5V; accepts up to ±15V.

Pins 35 and 36 are internally shorted together.

ROFSB (Pins 37, 38): Bipolar Offset Resistor for DAC B.

These pins provide the translation of the output voltage

range for bipolar spans. Accepts up to ±15V; for normal

operation tie to the positive reference voltage at RINB (Pins

31, 32). Pins 37 and 38 are internally shorted together.

RFBB (Pins 39, 40): DAC B Feedback Resistor. For normal

operation tie to the output of the I/V converter amplifier for

DAC B (see Typical Application). The DAC output current

from IOUT1B flows through the feedback resistor to the

RFBB pins. Pins 39 and 40 are internally shorted together.

IOUT1B (Pin 41): DAC B Current Output. This pin is a virtual

ground when the DAC is operating and should reside at

0V. For normal operation tie to the negative input of the

I/V converter amplifier for DAC B (see Typical Application).

VOSADJB (Pin 42): DAC B Offset Adjust Pin. This voltage-

control pin can be used to null unipolar offset or bipolar

zero error. The offset change expressed in LSB is the same

for any output range. See System Offset and Gain Adjust-

ments in the Operation section. Tie to ground if not used.

VOSADJA (Pin 43): DAC A Offset Adjust Pin. This voltage-

control pin can be used to null unipolar offset or bipolar

zero error. The offset change expressed in LSB is the same

for any output range. See System Offset and Gain Adjust-

ments in the Operation section. Tie to ground if not used.

IOUT1A (Pin 44): DAC A Current Output. This pin is a virtual

ground when the DAC is operating and should reside at

0V. For normal operation tie to the negative input of the

I/V converter amplifier for DAC A (see Typical Application).

RFBA (Pins 45, 46): DAC A Feedback Resistor. For normal

operation tie to the output of the I/V converter amplifier for

DAC A (see Typical Application). The DAC output current

from IOUT1A flows through the feedback resistor to the

RFBA pins. Pins 45 and 46 are internally shorted together.

ROFSA (Pins 47, 48): Bipolar Offset Resistor for DAC A.

This pin provides the translation of the output voltage

range for bipolar spans. Accepts up to ±15V; for normal

operation tie to the positive reference voltage at RINA

(Pins 5, 6). Pins 47 and 48 are internally shorted together.

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