Datasheet

UCD9244
www.ti.com SLVSAL6A –NOVEMBER 2010–REVISED FEBRUARY 2011
ADC MONITORING INTERVALS AND RESPONSE TIMES
The ADC operates in a continuous conversion sequence that measures each rail's output voltage and output
current, plus six other variables (input voltage, internal temperature, and four external temperature sensors). The
length of the sequence is determined by the number of output rails (NumRails) configured for use. The time to
complete the monitoring sampling sequence is give by the formula: t
ADC_SEQ
= t
ADC
× (2 × NumRAILS + 6)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
t
ADC
ADC single-sample time 3.84 µs
t
ADC_SEQ
ADC sequencer interval Min = 2 × 1 Rail + 6 = 8 samples 30.72 53.76 µs
Max = 2 × 4 Rails + 6 = 14 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 1 ms
t
TEMP
Temperature monitoring interval 100 ms
t
AUXADC
Auxiliary ADC monitoring interval 100 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.
MAX MAX
PARAMETER TEST CONDITIONS TYP UNIT
no VID /w VID
(1)
t
OVF
, Over-/under-voltage fault response time Normal regulation, no PMBus activity, 250 800 µs
t
UVF
during normal operation
4 stages enabled
t
OVF
, Over-/under-voltage fault response time, During data logging to nonvolatile 800 1000 µs
t
UVF
during data logging memory
(2)
t
OVF
, Over-/under-voltage fault response time, During tracking and soft-start ramp. 400 µs
t
UVF
when tracking or sequencing enable
t
OCF
, Over-/under-current fault response time Normal regulation, no PMBus activity, 100 + 5000 µs
t
UCF
during normal operation
4 stages enabled 75% to 125% current (600 × NRails)
step
(3)
t
OCF
, Over-/under-current fault response time, During data logging to nonvolatile 600 + 5000 µs
t
UCF
during data logging memory 75% to 125% current step
(600 × NRails)
t
OTF
Over-temperature fault response time Temperature rise of 10°C/sec, at OT 1.60 sec
threshold
t
3-State
Time to tristate the PWM output after a DRIVER_CONFIG = 0x01 5.5 µs
shutdown is initiated
(1) Controller receiving VID commands at a rate of 4000 msg/sec.
(2) During a STORE_DEFAULT_ALL command, which stores the entire configuration to nonvolatile memory, the fault detection latency can
be up to 10 ms.
(3) Because the current measurement is averaged with a smoothing filter, the response time to an over-current condition depends on a
combination of the time constant (τ) from Table 3, the recent measurement history, and how much the measured value exceeds the
over-current limit.
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