MAX11014_08 Datasheet, PDF (22/70 Pages) Maxim Integrated Products – Automatic RF MESFET Amplifier Drain-Current Controllers

Automatic RF MESFET Amplifier
Drain-Current Controllers
ACQ
ADCIN1,
ADCIN2
HOLD
REFADC
DAC
AGND
CIN+
CIN-
COMPARATOR
ACQ
AGND
HOLD
ACQ
HOLD
AV_DD / 2
Figure 8. ADC Equivalent Input Circuit
filter that limits the analog-input bandwidth.
Analog Input Protection
Internal ESD protection diodes clamp ADCIN1/ADCIN2
to AV_DD and AGND, allowing them to swing from
(AGND - 0.3V) to (AV_DD + 0.3V) without damage.
However, for accurate conversions near full scale, the
inputs must not exceed AV_DD by more than 50mV or be
lower than AGND by 50mV. If an analog input voltage
exceeds the supplies, limit the input current to 2mA.
Temperature Measurements
The MAX11014/MAX11015 measure their internal die
temperature and two external remote-diode tempera-
tures. Write to the ADC conversion register to com-
mand a temperature conversion. See Table 19. Set the
CH6 bit to 1 to calculate the remote-diode DXP2/DXN2
temperature sensor reading and load the data into the
FIFO. Set the CH1 bit to 1 to calculate the remote-diode
DXP1/DXN1 temperature-sensor reading and load the
data into the FIFO. Set the CH0 bit to 1 to calculate the
internal die temperature-sensor reading and load the
data into the FIFO. Temperature data is output in
signed two’s-complement format at DOUT in SPI mode
and SDA in I²C mode. See Figure 22 for the tempera-
ture transfer function.
The MAX11014/MAX11015 perform internal tempera-
ture measurements with a diode-connected transistor.
The diode bias current changes from 66µA to 4µA to
produce a temperature-dependent bias voltage differ-
ence. The second conversion result at 4µA is subtract-
ed from the first at 66µA to calculate a digital value that
is proportional to absolute temperature. The stored
data result is the above digital code minus an offset to
adjust from Kelvin to Celsius. The reference voltage for
the temperature measurements is derived from the
internal reference source to ensure the temperature
calibration of 1 LSB corresponding to +0.125°C.
For external temperature readings, connect an npn
transistor between DXP_ and DXN_. Connect the base
and collector together as shown in Figure 4 to form a
base-emitter pn junction. The MAX11014/MAX11015
feature an ALARM output that trips when the internal or
external temperature rises above an upper threshold
value or drops below a lower threshold value. Set the
high and low temperature thresholds through the chan-
nel 1/channel 2 high/low temperature ALARM threshold
registers. See Tables 3, 4, and 5.
The temperature-sensing circuits power up for the first
temperature measurement in an ADC conversion scan.
The temperature-sensing block remains on until the
end of the scan to avoid an additional 50µs power-up
delay for each individual temperature channel. See the
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