MAX11014 Datasheet, PDF (53/69 Pages) Maxim Integrated Products – Automatic RF MESFET Amplifier Drain-Current Controllers

Automatic RF MESFET Amplifier
Drain-Current Controllers
111...111
111...110
111...101
FULL-SCALE TRANSITION
FS = V_REFADC
1 LSB = V_REFADC / 4096
011....111
011....110
000...011
000...010
000...001
000...000
0123
FS - 3/2 LSB ^FS
INPUT VOLTAGE (LSB)
Figure 21. ADC Transfer Function
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 I²C
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.
000....010
000....001
000....000
111....111
111....110
111....101
100....001
100....000
-256°C
0
TEMPERATURE °C
+255.5°C
Figure 22. Temperature Transfer Function
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 I²C 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
complement. 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 tem-
perature measurements.
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:
V_PGAOUT = V_REFADC − [4 x (V_RCS + − V_RCS −) + 12mV]
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