LTC2970-1 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2970-1' PDF : 36 Pages View PDF
LTC2970/LTC2970-1
U
OPERATIO
13. One Time Power Supply Voltage Servo
The one time voltage servo feature allows the LTC2970 to
servo an external power supply to a programmed value
and then stop updating the IDAC once the target value
has been reached.
Procedure:
Follow procedure for hard connecting or soft connecting
the LTC2970 to power supply trim pin; when updating
CHn_A_IDAC(), Chn_a_idac_servo_repeat should be de-
asserted low. The servo channel’s IDAC must be enabled
before Chn_a_servo_en may be set high.
Update CHn_A_IDAC() with Chn_a_idac_servo_repeat = 0.
This step may be skipped if Chn_a_idac_servo_repeat was
cleared low during the soft or hard connect procedure.
Update FAULT_EN() with Fault_en_chn_a_servo = 0. This
prevents the LTC2970 from reinitiating a servo after an
over-voltage or under-voltage fault.
Determine the target servo voltage, Chn_a_servo[14:0].
Update CHn_A_SERVO() register with Chn_a_servo_en
= 1, and Chn_a_servo[14:0].
LTC2970 response: The LTC2970 will increment, decrement
or hold Chn_a_idac[7:0] in order to match the measured
value of (VINn_AP-VINn_AM) to Chn_a_servo[14:0]. The
servo procedure will end when the internal Chn_a_servo_
done flag is set (see “Continuous Power Supply Voltage
Servo”). At this point the IDAC is either programmed to
the appropriate servo value or faulted.
Rules:
All “Continuous Power Supply Voltage Servo” rules
apply.
14. One Time Power Supply Voltage Servo with
Repeat On Fault
The LTC2970 one time voltage servo feature may be
modified to allow the LTC2970 to perform an additional
power supply servo operation after an under-voltage or
over-voltage fault is detected on the servo channel.
Procedure:
Follow procedure outlined for “One Time Power Supply
Voltage Servo”.
Update FAULT_EN() with Fault_en_chn_a_servo = 1.
Enable detection of the appropriate instantaneous faults
for all servo channels; see “Generating and Monitoring
Instantaneous Faults”.
LTC2970 response: Any time an instantaneous under-
voltage or over-voltage fault is detected on the servo
channel (Fault_ov_a_chn or Fault_uv_a_chn), the internal
Chn_a_servo_done flag for that channel is cleared, and
the LTC2970 will perform a complete one time servo. This
allows the LTC2970 to precisely restore the power supply
to the target servo value, after it has drifted beyond a user
defined operating window.
Rules:
All “Continuous Power Supply Voltage Servo” rules
apply.
During a permanent under-voltage or over-voltage fault
the LTC2970 will continuously try to correct the faulted
channel, after each failed attempt all other channels that
need monitoring by the ADC will be serviced.
15. Configuring ADC to Monitor Input Channels and
Internal Temperature Sensor
The LTC2970 is able to perform ADC conversions on any
combination of seven different input channels. A channel
is converted if its associated ADC_MON() bit is set high.
Refer to Table 7 for details.
Procedure:
Update ADC_MON() with the control bit of each channel
that is to be monitored set high.
LTC2970 response: All enabled channels will be sequen-
tially converted. The result of the most recent conversion
may be read from the ADC result register. Each time a
conversion is completed the new data bit associated with
the result register is asserted high. The new data bit is
29701fc
24
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