AD8555ACP-R2 Analog Devices Inc, AD8555ACP-R2 Datasheet - Page 21

• Manufacturer Part Number: AD8555ACP-R2
• Description: IC AMP CHOPPER 2MHZ 10MA 16LFCSP
• Manufacturer: Analog Devices Inc
• Series: DigiTrim®r

Specifications of AD8555ACP-R2

• Rohs Status: RoHS non-compliant
• Amplifier Type: Chopper (Zero-Drift)
• Number Of Circuits: 1
• Slew Rate: 1.2 V/µs
• Gain Bandwidth Product: 2MHz
• Current - Input Bias: 16nA
• Voltage - Input Offset: 2µV
• Current - Supply: 2mA
• Current - Output / Channel: 10mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-LFCSP
• Output Type: -
• -3db Bandwidth: -

Initial State
Initially, all the polysilicon fuses are intact. Each parameter has
the value 0 assigned (see Table 12).
Table 12. Initial State before Programming
Second Stage Gain Code = 0
First Stage Gain Code = 0
Output Offset Code = 0
Master Fuse = 0
When power is applied to a device, parameter values are taken
either from internal registers if the master fuse is not blown or
from the polysilicon fuses if the master fuse is blown.
Programmed values have no effect until the master fuse is
blown. The internal registers feature power-on reset so that
unprogrammed devices enter a known state after power-up;
power-on reset occurs when VDD is between 0.7 V and 2.2 V.
Simulation Mode
The simulation mode allows any parameter to be changed tem-
porarily. These changes are retained until the simulated value is
reprogrammed, the power is removed, or the master fuse is
blown. Parameters are simulated by setting Field 1 to 01, select-
ing the desired parameter in Field 2, and the desired value for
the parameter in Field 4. Note that a value of 11 for Field 2 is
ignored during the simulation mode. Examples of temporary
settings follow:
• By setting the second stage gain code (Parameter 00) to 011
• By setting the first stage gain code (Parameter 01) to 000 1011
• Set the output offset code (Parameter 10) to 0100 0000 and
Programming Mode
Intact fuses give a bit value of 0. Bits with a desired value of 1
need to have the associated fuse blown. Since a relatively large
current is needed to blow a fuse, only one fuse can be reliably
blown at a time. Thus, a given parameter value may need sever-
al 38-bit words to allow reliable programming. A 5.5 V supply is
required when blowing fuses to minimize the on resistance of
the internal MOS switches that blow the fuse. The power supply
must be able to deliver 250 mA of current, and at least 0.1 μF of
decoupling capacitance is needed across the power pins of the
device. A minimum period of 1 ms should be allowed for each
and the second stage gain to 50, 1000 0000 0001 01 00 10
0000 0011 0111 1111 1110 is the result.
and the first stage gain to 4.166, 1000 0000 0001 01 01 10
0000 1011 0111 1111 1110 is the result.
A first stage gain of 4.166 with a second stage gain of 50 gives
a total gain of 208.3. This gain has a maximum tolerance of
2.5%.
the output offset to 1.260 V when VDD = 5 V and VSS = 0 V.
This output offset has a maximum tolerance of 0.8%: 1000
0000 0001 01 10 10 0100 0000 0111 1111 1110.
Second Stage Gain = 17.5
First Stage Gain = 4.0
Output Offset = VSS
Master Fuse Not Blown
Rev. A | Page 21 of 28
fuse to blow. There is no need to measure the supply current
during programming; the best way to verify correct program-
ming is to use the read mode to read back the programmed
values and to remeasure the gain and offset to verify these
values. Programmed fuses have no effect on the gain and output
offset until the master fuse is blown; after blowing the master
fuse, the gain and output offset are determined solely by the
blown fuses and the simulation mode is permanently deacti-
vated.
Parameters are programmed by setting Field 1 to 10, selecting
the desired parameter in Field 2, and selecting a single bit with
the value 1 in Field 4.
As an example, suppose the user wants to permanently set the
second stage gain to 50. Parameter 00 needs to have the value
0000 0011 assigned. Two bits have the value 1, so two fuses need
to be blown. Since only one fuse can be blown at a time, the
code 1000 0000 0001 10 00 10 0000 0010 0111 1111 1110 can be
used to blow one fuse. The MOS switch that blows the fuse
closes when the complete packet is recognized and opens when
the start-of-packet, dummy, or end-of-packet fields are no long-
er valid. After 1 ms, the second code 1000 0000 0001 10 00 10
0000 0001 0111 1111 1110 can be entered to blow the second
fuse.
To set the first stage gain permanently to a nominal value of
4.151, Parameter 01 needs to have the value 000 1011 assigned.
Three fuses need to be blown, and the following codes can be
used, with a 1 ms delay after each code:
1000 0000 0001 10 01 10 0000 1000 0111 1111 1110
1000 0000 0001 10 01 10 0000 0010 0111 1111 1110
1000 0000 0001 10 01 10 0000 0001 0111 1111 1110
To set the output offset permanently to a nominal value of
1.260 V when VDD = 5 V and VSS = 0 V, Parameter 10 needs to
have the value 0100 0000 assigned. One fuse needs to be blown,
and the following code can be used: 1000 0000 0001 10 10 10
0100 0000 0111 1111 1110.
Finally, to blow the master fuse to deactivate the simulation
mode and prevent further programming, the code 1000 0000
0001 10 11 10 0000 0001 0111 1111 1110 can be used.
There are a total of 20 programmable fuses. Since each fuse
requires 1 ms to blow, and each serial word can be loaded in
2.3 ms, the maximum time needed to program the fuses can be as
low as 66 ms.
Parity Error Detection
A parity check is used to determine whether the programmed
data of an AD8555 is valid, or whether data corruption has
occurred in the nonvolatile memory. Figure 52 shows the sche-
matic implemented in the AD8555.
AD8555