MAX11014 Datasheet, PDF (57/69 Pages) Maxim Integrated Products – Automatic RF MESFET Amplifier Drain-Current Controllers

Automatic RF MESFET Amplifier
Drain-Current Controllers
HIGH
THRESHOLD
REGISTER
LOW
THRESHOLD
REGISTER
ALARM
COMPARATOR
(ACTIVE-LOW)
ALARM INTERRUPT
(ACTIVE-LOW)
VOLTAGE OR
TEMPERATURE
MEASUREMENT VALUE
READ ALARM
FLAG REGISTER
Figure 27. ALARM Hysteresis-Mode Timing Example
READ ALARM
TIME
FLAG REGISTER
high set ALARM threshold register value. See Figure
26. If an ADC output value exceeds its respective
ALARM high threshold register value, the ALARM out-
put triggers. The alarm condition remains in place until
the measured value falls below the low threshold value.
Figure 27 details a hysteresis-mode timing example.
When operating in interrupt mode, the ALARM output
triggers when the measured ADC output value exceeds
either the high or low threshold. However, in interrupt
mode, the ALARM output remains active until reading
the ALARM flag register. Reading the ALARM flag reg-
ister resets the flag bits and the ALARM output.
The default values for the high and low threshold regis-
ters are the extremes of the measured range (all 1s or
all 0s, respectively). The ALARM output can be config-
ured to be open-drain or push-pull and active-high or
active-low through the hardware ALARM configuration
register. See Table 12. At power-up, the ALARM output
is configured as an active-high output that operates in
interrupt mode.
Automatic GATE Clamping
Configure the ALARM output to clamp the GATE1 out-
put to ACLAMP1 or GATE2 output to ACLAMP2 in
response to an alarm condition through the hardware
ALARM configuration register. See Table 12c. Set the
ALM_CLMP_ bits, D5–D2, to clamp the respective
channel’s GATE output.
Each channel has four possible ALM_CLMP1/
ALM_CLMP0 values:
• ALM_CLMP1/ALM_CLMP0 = 00
Power-on reset state. GATE_ clamps through a
series 2.4kΩ resistor to the ACLAMP_, regardless
of any alarm condition. Reset these 2 bits before
attempting to change the DAC voltage.
• ALM_CLMP1/ALM_CLMP0 = 01
The automatic GATE_ clamp is disabled in this mode.
The GATE_ outputs are not affected by any alarm
conditions. The ALARM output function operates nor-
mally (samples beyond their thresholds still cause
alarm flags to be set and ALARM behaves according
to the comparator/interrupt mode).
• ALM_CLMP1/ALM_CLMP0 = 10
This mode provides fully automatic clamping. Prior to
an alarm condition, the GATE_ voltage is controlled
by the sense voltage (MAX11014) or the DAC setting
(MAX11015). When an alarm condition triggers, the
GATE_ voltage clamps to ACLAMP_. The clamp is
applied as long as the alarm condition is valid. The
GATE_ clamp is released when a subsequent ADC
conversion clears the alarm condition. The GATE_
voltage is then restored to the sense voltage/DAC set-
ting. Configure the ALARM output in comparator
mode to assert when the GATE_ clamp is active.
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