TPS546C23 Datasheet, PDF (26/97 Pages) Texas Instruments – 4.5-V to 18-V, 35-A Stackable Synchronous Buck Converters With PMBus

TPS546C23
SLUSCC7A – JULY 2016 – REVISED AUGUST 2016
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7.3.18 TON_MAX Fault
The TON_MAX_FAULT_LIMIT command sets an upper limit, in milliseconds, on how long the unit can attempt to
power up the output without reaching the output undervoltage fault limit. The devices differentiate a startup UV
fault and a regulation UV fault by implementing the TON_MAX_FAULT_LIMIT command. The
TON_MAX_FAULT_LIMIT command can allow the devices more time than the soft-start time defined by
TON_RISE to come into regulation and the UV detection is essentially delayed up to the
TON_MAX_FAULT_LIMIT time. For more details, see the TON_MAX_FAULT_LIMIT (62h) section.
7.3.19 Power Good (PGOOD) Indicator
When the output voltage remains within the PGOOD window after the start-up period, PGOOD as an open-drain
output is released, and rises to an externally supplied logic level. The PGOOD window is defined by OV warning
limit and UV warning limit in PCT_OV_UV_WRN_FLT_LIMITS (MFR_SPECIFIC_07) (D7h), which can be
programmed through the PMBus interface, as shown in Figure 34. The PGOOD pin pulls low upon any fault
condition on default. Please refer to Table 2 for the possible sources to pull down the PGOOD pin.
The PGOOD signal can be connected to the CNTL pin of another device to provide additional controlled turnon
and turnoff sequencing.
The OVW or PGOOD signal trips when the FB pin is prebiased to higher than 5% about the regulation level. This
level of prebias is unusual and it is beneficial to flag a warning in this situation.
OV Fault
OV Warn
VOUT_COMMAND
OVW
Hysteresis
UV Warn
FB
UV Fault
UVW
Hysteresis
PGOOD
(non-latch)
Time
Figure 34. PGOOD Threshold and Hysteresis
NOTE
Pulling PGOOD pin high before the devices gets input power could cause PGOOD pin
going high due to the limited pulldown capability in un-powered condition. If this is not
desired, increase the pullup resistance or reduce the external pullup supply voltage.
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