Datasheet

MAX11014/MAX11015
Automatic RF MESFET Amplifier
Drain-Current Controllers
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indicated by channel tag 1110 (rather than the usual
ADC channel tag). In this case, only that particular data
item is corrupted and all other FIFO contents remain
valid and can be accessed with subsequent reads.
Read the FIFO quickly enough to prevent overflow
conditions to entirely avoid the risk of data corruption. At
fast serial-interface clock rates, it is possible to read data
from the FIFO faster than the ADC loads it. Set a continu-
ous ADC scan in progress and continuously read the
FIFO. Assuming the FIFO is being emptied more quickly
than it is being filled, the continuous FIFO reads supply a
mixture of empty channel tags (1111 and the flag regis-
ter value), mixed in with the valid ADC results. Separate
the valid ADC results from the flag register data based
on the 4-bit channel tag.
SRAM LUT Read Mode
After an LUT data register read command, data from
the SRAM LUTs is copied into the FIFO. Load the data
from the FIFO to DOUT in SPI mode and SDA in I
2
C
mode by reading the FIFO. If SRAM LUT data is written
to the FIFO faster than its read out, the FIFO fills up.
The copying of data is suspended until the FIFO is read
again. If the FIFO is read more quickly than the SRAM
LUT loads the values, the data is interspersed with error
channel tags (1111 and the flag register value) and
valid LUT data.
Output Data Format
All conversion data results are output in 2-byte format,
MSB first. Data transitions on DOUT on the falling
edges of SCLK in SPI mode. Data transitions on SDA
on the rising edge of SCL in I
2
C mode. Figures 10, 18,
and 19 illustrate the MAX11014/MAX11015’s read tim-
ing. See Figures 21 and 22 for ADC and temperature
transfer functions, respectively.
ADC Transfer Function
Data is output in straight binary format, with the excep-
tion of temperature results/alarms, which are two’s com-
plement. Figure 21 shows the unipolar transfer function
for single-ended inputs. Code transitions occur halfway
between successive-integer LSB values. Output coding
is binary, with 1 LSB = V
REFADC
/ 2.5V for unipolar
operation, and 1 LSB = +0.125°C for temperature mea-
surements.
PGAOUT Outputs
The PGAOUT output voltages are derived from a sense
voltage conversion. The dual current-sense amplifiers
amplify the voltage between RCS_+ and RCS_- by four
and add an offset voltage (+12mV nominally). The cur-
rent-sense amplifiers scale voltages up to +625mV. The
MAX11014’s Class A control loop detailed in Figure 5.
The MAX11015’s Class AB analog control is detailed in
Figure 6. Calculate the PGAOUT_ voltage with the fol-
lowing equation:
VV xVV mV
PGAOUT REFADC RCS RCS_ __
[ ( ) ]=− +−−+412
FULL-SCALE TRANSITION
INPUT VOLTAGE (LSB)
OFFSET BINARY OUTPUT CODE (LSB)
FS - 3/2 LSB
0
000...000
000...001
000...010
000...011
111...111
111...110
111...101
FS = V
REFADC
1 LSB = V
REFADC
/ 4096
FS
123
OUTPUT CODE
011....111
TEMPERATURE °C
011....110
000....001
111....101
100....001
100....000
111....111
111....110
000....000
0
000....010
-256°C +255.5°C
Figure 21. ADC Transfer Function
Figure 22. Temperature Transfer Function