AD5381
Table 16. Control Register Contents
MSB
CR11
CR10
Control Register Write/Read
REG1 = REG0 = 0, A5–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 register data.
Rev. A | Page 23 of 36
CR9
CR8
CR7
CR6
CR5
CR4
CR3
CR2
CR1
LSB
CR0
Control Register Contents
CR11:
Power-Down Status. This bit is used to configure the
output amplifier state in power down.
CR11 = 1. Amplifier output is high impedance (default on
power-up).
CR11 = 0. Amplifier output is 100 k to ground.
CR10:
REF Select. This bit selects the operating internal
reference for the AD5381. CR10 is programmed as follows:
CR10 = 1: Internal reference is 2.5 V (AD5381-5 default), the
recommended operating reference for AD5381-5.
CR10 = 0: Internal reference is 1.25 V (AD5381-3 default),
the recommended operating 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 (default on power up).
CR7:
Channel Monitor Enable (see Channel Monitor Function)
CR7= 1: Monitor Enabled. This enables the channel monitor
function. After a write to the monitor channel in the SFR
register, the selected channel output is routed to the
MON_OUT pin. VOUT 39 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. This function is used to
monitor the AD5381’s internal die temperature when enabled.
The thermal monitor powers down the output amplifiers when
the temperature exceeds 130°C. This function can be used to
protect the device in cases where power dissipation may be
exceeded if a number of output channels are simultaneously
short-circuited. A soft power-up will re-enable the output
amplifiers if the die temperature has dropped below 130°C.
CR6 = 1: Thermal Monitor Enabled.
CR6 = 0: Thermal Monitor Disabled (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 register for each DAC. Control register bits CR4 to CR0 are
used to enable individual groups of eight channels for opera-
tion in toggle mode. A Logic 1 written to any bit enables a group
of channels; a Logic 0 disables a group. LDAC is used to toggle
between the two registers.
Table 17.
CR Bit
CR4
CR3
CR2
CR1
CR0
Channel Monitor Function
REG1 = REG0 = 0, A5–A0 = 001010
Group
4
3
2
1
0
Channels
32–39
24–31
16–23
8–15
0–7
DB11–DB6 = Contain data to address the monitored channel.
A channel monitor function is provided on the AD5381. This
feature, which consists of a multiplexer addressed via the
interface, allows any channel output to be routed to the
MON_OUT pin for monitoring using an external ADC. In
channel monitor mode, VOUT 39 becomes the MON_OUT pin,
to which all monitored pins are routed. The channel monitor
function must be enabled in the control register before any
channels are routed to MON_OUT. On the AD5381, DB11 to
DB6 contain the channel address for the monitored channel.
Selecting channel address 63 three-states MON_OUT.