AD5750 datasheet(17/25 Pages) AD

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Preliminary Technical Data

AD5750

Rev. PrC | Page 17 of 25

CURRENT OUTPUT ARCHITECTURE

The voltage input from the analog input VIN core (0-4.096v) is

either converted to a current (see Figure 12) which is then

mirrored to the supply rail so that the application simply sees a

current source output with respect to an internal reference

voltage or it is buffered and scaled to output a software

selectable unipolar or bipolar voltage range (See Figure 13).

The Reference is used to provide internal offsets for range and

gain scaling. The selectable output range is programmable

through the digital interface.

IOUT

VREF

RSET

REXT2

IOUT

RANGE

SCALING

IOUT OPEN FAULT

VDD

VSS

REXT1

RANGE DECODE

FROM INTERFACE

VIN

VINT

Figure 11. Current Output Configuration

VIN

(0-4.096V)

VREF

+VSENSE

-VSENSE

VOUT RANGE

SCALING

VOUT SHORT FAULT

RANGE DECODE

FROM INTERFACE

VOUT

Figure 12. Voltage Output

Voltage Output Amplifier

The voltage output amplifier is capable of generating both

unipolar and bipolar output voltages. It is capable of driving a

load of 1 kΩ in parallel with 1.2 uF. The source and sink

capabilities of the output amplifier can be seen in Figure TBD.

The slew rate is 1 V/μs with a full-scale settling time of 10

μs.(10V step).

The current and voltage are output on separate pins and cannot

be output simultaneously. This allows the user to tie both the

current and voltage output pins together and configuring the

end system as “one channel” output.

Driving Large Capacitive Loads

The voltage output amplifier is capable of driving capacative

loads of up to 1uF with the addition of a non-polarised 4nF

compensation capacitor between the CCOMP1 and CCOMP2 pins.

Without the compensation capacitor, up to 20nF capacitive

loads can be driven.

POWER ON STATE OF AD5750

On Power-up, the AD5750 will sense whether hardware or

software mode is loaded and set the power up conditions

accordingly.

In software SPI mode, the part will power up with all outputs

disabled (OUTEN bit=0). In disabled mode, both the current

and voltage outputs are put into tri-state mode. The user will

have to set the OUTEN bit in the control register to enable the

output and in the same write the user will also set the output

range configuration using the range bits.

If hardware mode is selected, the part will power up to the

conditions defined by the range bits and the status of the

OUTEN pin. It is recommended to keep the output disabled

when powering up the part in hardware mode.

RESET:

The AD5750 contains a reset function.

In Software mode, the part can be reset using the RESET pin

(active low) or the RESET bit (RESET=1). A reset will disable

both the current and voltage outputs and put them in tri-state

mode. The user will have to write to the OUTEN bit to enable

the output and in the same write the user will also set the output

range configuration. The RESET pin is a level sensitive input -

the part will stay in RESET mode as long as RESET pin is low.

The RESET bit will clear to zero following a RESET command

to the control register.

In hardware mode, there is no RESET. If using the part in

hardware mode the RESET pin should be tied high.

OUTEN

In Software mode, the output can be enabled/disabled using the

OUTEN bit in the control register. When the output is disabled,

both the current and voltage channels both go into tri-state. The

user will have to set the OUTEN bit to enable the output and at

this time the user will also set the output range configuration.

In Hardware mode, the output can be enabled/disabled using

the OUTEN pin. When the output is disabled, both the current

and voltage channels both go into tri-state. The user will have

to write to the OUTEN pin to enable the output. It is

recommended that the output be disabled when changing the

ranges.

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