Datasheet

UCD9248
SLVSA33A JANUARY 2010REVISED AUGUST 2012
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ADC MONITORING INTERVALS AND RESPONSE TIMES
The ADC operates in a continuous conversion sequence that measures each rail's output voltage, each power
stage's output current, plus four other variables (external temperature, Internal temperature, input voltage and
current, and tracking input voltage). The length of the sequence is determined by the number of output rails
(NumRails) and total output power stages (NumPhases) configured for use. The time to complete the monitoring
sampling sequence is give by the formula:
t
ADC_SEQ
= t
ADC
× (NumRAILS + NumPHASE + 4)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
t
ADC
ADC single-sample time 3.84 µs
Min = 1 Rail + 1 Phase + 4 = 6 samples Max = 4
t
ADC_SEQ
ADC sequencer interval 23.04 61.44 µs
Rails + 8 Phases + 4 = 16 samples
The most recent ADC conversion results are periodically converted into the proper measurement units (volts,
amperes, degrees), and each measurement is compared to its corresponding fault and warning limits. The
monitoring operates asynchronously to the ADC, at intervals shown in the table below.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
t
Vout
Output voltage monitoring interval 200 µs
t
Iout
Output current monitoring interval 200 × NRails µs
t
Vin
Input voltage monitoring interval 2 ms
t
Iin
Input current monitoring interval 2 ms
t
TEMP
Temperature monitoring interval 100 ms
t
Ibal
Output current balancing interval 2 ms
Because the ADC sequencer and the monitoring comparisons are asynchronous to each other, the response
time to a fault condition depends on where the event occurs within the monitoring interval and within the ADC
sequence interval. Once a fault condition is detected, some additional time is required to determine the correct
action based on the FAULT_RESPONSE code, and then to perform the appropriate response. The following
table lists the worse-case fault response times.
PARAMETER TEST CONDITIONS MAX TIME UNIT
Over-/under-voltage fault response time during Normal regulation, no PMBus activity, 8
300 µs
normal operation stages enabled
Over-/under-voltage fault response time, during
t
OVF
, t
UVF
During data logging to nonvolatile memory
(1)
800 µs
data logging
Over-/under-voltage fault response time, when
During tracking and soft-start ramp. 400 µs
tracking or sequencing enable
Over-/under-current fault response time during Normal regulation, no PMBus activity, 8
100 + (600 × NRails) µs
normal operation stages enabled 75% to 125% current step
Over-/under-current fault response time, during During data logging to nonvolatile memory
t
OCF
, t
UCF
600 + (600 × NRails) µs
data logging 75% to 125% current step
Over-/under-current fault response time, when During tracking and soft start ramp 75% to
300 + (600 × NRails) µs
tracking or sequencing enable 125% current step
Temperature rise of 10°C/sec,
t
OTF
Over-temperature fault response time 2.5 S
OT threshold = 100°C
(1) During a STORE_DEFAULT_ALL command, which stores the entire configuration to nonvolatile memory, the fault detection latency can
be up to 10 ms.
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