Datasheet

AD5522 Data Sheet
Rev. E | Page 46 of 64
WRITE SYSTEM CONTROL REGISTER
The system control register is accessed when the PMU channel
address bits (PMU3 to PMU0) and the mode bits (MODE1 and
MODE0) are all 0s. This register allows quick setup of various
functions in the device. The system control register operates on
a per-device basis.
Table 21. System Control Register Bits—Bit B28 to Bit B15
B28 B27 B26 B25 B24 B23 B22 B21 B20 B19 B18 B17 B16 B15
RD/
WR
PMU3 PMU2 PMU1 PMU0 MODE1
MODE0
CL3 CL2 CL1 CL0 CPOLH3 CPOLH2 CPOLH1
Table 22. System Control Register Bits—Bit B14 to Bit B0
B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1
1
B0
1
CPOLH0 CPBIASEN DUTGND/CH Guard
ALM
Clamp
ALM
INT10K Guard
EN
GAIN1 GAIN0 TMP
enable
TMP1 TMP0 Latched 0 0
1
Bit B1 and Bit B0 are unused data bits.
Table 23. System Control Register Functions
Bit Bit Name Description
28 (MSB) RD/
WR
When low, a write function takes place to the selected register; setting the RD/
WR
bit high initiates a readback
sequence of the PMU, alarm status, comparator status, system control, or DAC register, as determined by the
address bits.
27 PMU3 Set Bit PMU3 to Bit PMU0 to 0 to address the system control register.
26 PMU2
25 PMU1
24 PMU0
23 MODE1 Set the MODE1 and MODE0 bits to 0 to address the system control register.
22 MODE0
System Control Register-Specific Bits
21 CL3 Current or voltage clamp enable. Bit CL3 to Bit CL0 enable and disable the current or voltage clamp function per
channel (0 = disable; 1 = enable). The clamp enable function is also available in the PMU register on a per-
channel basis. This dual functionality allows flexible enabling or disabling of this function. When reading back
information about the status of the clamp enable function, the data that was most recently written to the clamp
register is available in the readback word from either the PMU register or the system control register.
20
CL2
19 CL1
18 CL0
17 CPOLH3 Comparator output enable. By default, the comparator outputs are high-Z on power-on. A 1 in each bit position
enables the comparator output for the selected channel. Bit 13 (CPBIASEN) must be enabled to power on the
comparator functions. The comparator enable function is also available in the PMU register on a per-channel
basis. This dual functionality allows flexible enabling or disabling of this function. When reading back information
about the status of the comparator enable function, the data that was most recently written to the comparator
status register is available in the readback word from either the PMU register or the system control register.
16 CPOLH2
15 CPOLH1
14 CPOLH0
13 CPBIASEN Comparator enable. By default, the comparators are powered down when the device is powered on. To enable
the comparator function for all channels, write a 1 to this bit. A 0 disables the comparators and shuts them
down. The comparator output enable bits (CPOLHx, Bit 17 to Bit 14) allow the user to turn on each comparator
output individually, enabling busing of comparator outputs.
12 DUTGND/CH DUTGND per channel enable. The GUARDINx/DUTGNDx pins are shared pins that can be configured to enable a
DUTGND per PMU channel or a guard input per PMU channel. Setting this bit to 1 enables DUTGND per
channel. In this mode, the pin functions as a DUTGND pin on a per-channel basis. The guard inputs are
disconnected from this pin and instead are connected directly to the MEASVHx line by an internal connection.
The default power-on condition is GUARDINx.
11 GUARD ALM Clamp and guard alarm functions share one open-drain alarm pin (
CGALM
). By default, the
CGALM
pin is
disabled. The guard ALM and clamp ALM bits allow the user to choose whether clamp alarm information, guard
alarm information, or both sets of alarm information are flagged by the
CGALM
pin. Set high to enable either
alarm function.
10 CLAMP ALM
9 INT10K Internal sense short. Setting this bit high allows the user to connect an internal sense short resistor of 10 kΩ
(4 kΩ + 2 kΩ switch + 4 kΩ) between the FOHx and the MEASVHx lines (SW7 is closed). Setting this bit high also
closes SW15, allowing the user to connect another 10 kΩ resistor between DUTGNDx and AGND.
8 Guard EN Guard enable. The guard amplifier is disabled on power-on; to enable the guard amplifier, set this bit to 1. If the
guard function is not in use, disabling it saves power (typically 400 μA per channel).