LTC2970-1 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2970-1' PDF : 36 Pages View PDF
U
OPERATIO
LTC2970-1 response: Each tracking enabled channel is soft
connected. The GPIO_CFG pin is released allowing it to be
pulled high. The LTC2970-1 waits tSETUP_TRACK to allow
GPIO_CFG to settle. For each tracking enabled channel,
the Chn_a_delay_track counter is decremented at a rate
of tDEC_TRACK. As soon as a channel’s tracking counter
reaches zero, the LTC2970-1 will begin stepping the value
of Chn_a_idac[7:0] by one count until the final value of
Chn_a_idac_track[7:0] is reached. The tracking enable bit
is then cleared for both channels (Chn_a_idac_track_en
= 0).
IO(): The I2C interface may then be used to set GPIO_1
and GPIO_0 low, disabling the power supplies.
Power Down Tracking Rules:
Power down tracking requests will be ignored until the
user has disabled the IDAC’s by setting Chn_a_idac_en =
0 for each tracking enabled channel.
Chn_a_idac_track_pol, Chn_a_idac_track_en, and ch0_
idac[7:0] updates will be ignored after IO(IO_track_start) is
asserted until tracking is complete and whenever tracking
range is configured; (GPIO_CFG high with either GPIO_0
or GPIO_1 asserted high).
12. Continuous Power Supply Voltage Servo
The continuous voltage servo feature allows the LTC2970
to servo an external power supply to a programmed
value. The voltage of the external supply is monitored
over Chn_A_ADC and compared to a target value stored
in Chn_a_servo. After each conversion, Chn_A_IDAC is
incremented by 1, decremented by 1, or held; whichever
brings or keeps the measured voltage closer to the targeted
servo value.
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 as-
serted high. The servo channel’s IDAC must be enabled
before Chn_A_servo_en can be set high.
LTC2970/LTC2970-1
Determine the target servo voltage, Chn_a_servo[14:0].
Update CHn_A_SERVO() with Chn_a_servo_en = 1, and
Chn_a_servo[14:0].
Update CHn_A_IDAC() with Chn_a_idac_servo_repeat =
1. This step may be skipped if Chn_a_idac_servo_repeat
was set high during the soft or hard connect procedure.
LTC2970 response: The LTC2970 will continuously in-
crement, 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].
Whenever the CHn_A_SERVO() register is updated an in-
ternal flag is cleared indicating that a successful servo has
not been completed. This internal flag, Chn_a_servo_done,
initially causes the ADC to operate in an accelerated 12-bit
mode. Once the channel reaches the servo target, the ADC
switches back to 14-bit mode for two conversions before
asserting Chn_a_servo_done high.
In continuous voltage servo mode the Chn_a_servo_done
flags allow the initial servo target to be reached quickly.
During this time, ADC conversions for all non-servo chan-
nels are temporarily inhibited.
Rules:
The IDAC associated with the servo channel must be
enabled. If Chn_a_idac_en is low the servo enable bit
Chn_a_servo_en is always forced low.
The IDAC associated with the servo channel must be con-
nected (Chn_a_idac_con = 1).
An IDAC fault may be generated during a continuous servo
operation. The LTC2970 will report the fault and continue
trying to servo that channel.
LTC2970-1 Only: There must be no pending tracking
commands. A pending tracking command will clear
Chn_a_servo_en.
LTC2970-1 Only: The tracking range must not be enabled;
(GPIO_CFG high with either GPIO_0 or GPIO_1 asserted
high). An enabled tracking range will clear Chn_a_servo_en
low.
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