AD5381BSTZ-5 datasheet(23/40 Pages) AD

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Data Sheet

AD5381

Rev. D | Page 23 of 40

Table 15. Control Register Contents

MSB

LSB

CR11

CR10

CR9

CR8

CR7

CR6

CR5

CR4

CR3

CR2

CR1

CR0

Control Register Write/Read

REG1 = REG0 = 0, A5 to A0 = 001100, R/W status determines

if the operation is a write (R/W = 0) or a read (R/W = 1). DB11

to DB0 contains the control registerdata.

Control Register Contents

CR11: Power-Down Status. This bit is used to configure the

output amplifier statein power-down.

CR11 = 1. Amplifier output is high impedance (defaulton

power-up).

CR11 = 0. Amplifier output is 100 kΩ to ground.

CR10: REF Select. This bit selects the operating internal

referencefor the AD5381. CR10 is programmed as follows:

CR10 = 1: Internal reference is 2.5 V (AD5381-5 default), the

recommendedoperating reference for AD5381-5.

CR10 = 0: Internal reference is 1.25 V (AD5381-3 default),

the recommendedoperating reference for AD5381-3.

CR9: Current Boost Control. This bit is used to boost the

current in the output amplifier, thereby altering its slew rate.

This bit is configured as follows:

CR9 = 1: Boost Mode On. This maximizes the bias current

in the output amplifier, optimizing its slew rate but increasing

the power dissipation.

CR9 = 0: Boost Mode Off (default on power-up). This

reduces the bias current in the output amplifier and reduces

the overall power consumption.

CR8: Internal/External Reference. This bit determines if the

DAC uses its internal reference or an externally applied

reference.

CR8 = 1: Internal Reference Enabled.The reference output

depends on data loaded to CR10.

CR8 = 0: External Reference Selected(defaulton power-up).

CR7: Channel Monitor Enable(see Channel Monitor Function

section).

CR7= 1: Monitor Enabled. This enablesthe channel monitor

function. After a write to the monitor channel in the SFR

MON_OUT pin. VOUT39 operates at the MON_OUT pin.

CR7 = 0: Monitor Disabled (default on power-up). When the

monitor is disabled, the MON_OUT pin assumes its normal

DAC output function.

CR6: Thermal Monitor Function. When enabled, this function

is used to monitor the internal die temperature of the AD5381.

The thermal monitorpowersdown the output amplifiers when

the temperature exceeds130°C. This function can be used to

protect the device in cases where power dissipation may be

exceeded if a number of outputchannels aresimultaneously

short-circuited. A soft power-up will re-enable the output

amplifiers if the die temperature hasdroppedbelow 130°C.

CR6 = 1: Thermal MonitorEnabled.

CR6 = 0: Thermal MonitorDisabled (default on power-up).

CR5: Don’t Care.

CR4 to CR0: Toggle Function Enable. This function allows the

user to toggle the output between two codes loaded to the A

and B registers for each DAC.Control Register Bits CR4 to CR0

are used to enableindividual groups of eight channels for

operation in toggle mode. A Logic1 written to any bit enables

a group of channels; a Logic0 disables a group. LDACis used

to toggle between the two registers.

Table 16.

CR Bit

Group

Channels

CR4

32–39

CR3

24–31

CR2

16–23

CR1

8–15

CR0

0–7

Channel Monitor Function

REG1 = REG0 = 0, A5 to A0 = 001010

DB11–DB6 = Contain data to address the monitoredchannel.

A channel monitor function is providedon the AD5381. This

feature, which consists of a multiplexeraddressed via the inter-

face, allows any channel output to be routed to the MON_OUT

pin for monitoring using an external ADC. In channel monitor

mode, VOUT39 becomes the MON_OUT pin, to which all

monitored pins arerouted. The channel monitor function must

be enabled in the control registerbeforeany channels arerouted

to MON_OUT. On the AD5381, DB11 to DB6 contain the

channel address forthe monitored channel. Selecting Channel

Address 63 three-states MON_OUT.

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