
Preliminary Technical Data
AD7760
Table 14. Status Register (Read Only)
Rev. PrN | Page 21 of 22
MSB
LSB
PART
1
PART
0
DIE
2
DIE
1
DIE
0
DVALID
LPWR
OVR
DL
OK
Filter
OK
U
Filter
BYP F3
BYP F1
DEC2
DEC1
DEC0
Bit
15,14
13-11
10
9
8
7
Mnemonic
PART1:0
DIE2:0
DVALID
LPWR
OVR
DL OK
Comment
Part Number. These bits will be constant for the AD7760.
Die Number. These bits will reflect the current AD7760 die number for identification purposes within a system.
Data Valid. This bit corresponds to the DVALID bit in the status word output in the second 16-bit read operation.
Low Power. If the AD7760 is operating in Low Power Mode, this bit is set to a 1.
If the current analog input exceeds the current overrange threshold, this bit will be set.
When downloading a user filter to the AD7760, a checksum is generated. This checksum is compared to the one
downloaded following the coefficients. If these checksums agree, this bit is set.
When a user-defined filter is in use, a checksum is generated when the filter coefficients pass through the filter. This
generated checksum is compared to the one downloaded. If they match, this bit is set.
If a user-defined filter is in use, this bit is set.
Bypass Filter 3. If Filter 3 is bypassed by setting the relevant bit in Control Register 1, this bit is also set.
Bypass Filter 1. If Filter 1 is bypassed by setting the relevant bit in Control Register 1, this bit is also set.
Decimation Rate. These correspond to the bits set in Control Register 1.
6
Filter OK
5
4
3
2-0
U Filter
BYP F3
BYP F1
DEC2:0
.
NON BIT-MAPPED REGISTERS
Offset Register (Address 0x0003, Default Value 0x0000)
The Offset Register uses 2’s Complement notation and is scaled such that 0x7FFF (maximum positive value) and 0x8000 (maximum
negative value) correspond to an offset of +0.78125% and -0.78125% respectively. Offset correction is applied after any gain correction.
Using the default gain value of 1.25 and assuming a reference voltage of 4.096V, the offset correction range is approximately ±25mV.
Gain Register (Address 0x0004, Default Value 0xA000)
The Gain Register is scaled such that 0x8000 corresponds to a gain of 1.0. The default value of this register is 1.25 (0xA000). This gives a
full scale digital output when the input is at 80% of V
REF
. This ties in with the maximum analog input range of ±80% of V
REF
Pk-Pk.
Over Range Register (Address 0x0005, Default Value 0xCCCC)
The Over Range register value is compared with the output of the first decimation filter to obtain an overload indication with minimum
propagation delay. This is prior to any gain scaling or offset adjustment. The default value is 0xCCCC which corresponds to 80% of V
REF
(the maximum permitted analog input voltage) Assuming V
REF
= 4.096V, the bit will then be set when the input voltage exceeds
approximately 6.55v pk-pk differential. Note that the over-range bit is also set immediately if the analog input voltage exceeds 100% of
V
REF
for more than 4 consecutive samples at the modulator rate.