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6.9
ON-OFF Control
PFH Series modules have an ON-OFF control pin, which is used to enable (turn on) or disable (turn off) the module. When
this pin is low, the PFH module is enabled. Internally, this pin is connected to a 10K pull-up resistor that is in series with
3.3V source. Due to noisy environments, it is strongly recommended that an external 0.1µF capacitor (Min) be placed from
the ON-OFF pin to SGND.
Maximum sink current of ON-OFF pin
Maximum low voltage for ON-OFF pin
Maximum high voltage of ON-OFF pin
ON-OFF pin references to Vout(-) Signal Ground.
The digital controller inside the module will remember the ON-OFF control sequence. If the module is enabled by ON-OFF
pin, then it must be turned off by ON-OFF pin. Trying to turn off the module by PMBus will be ignored. If the module is
enabled by PMBus control, then it must be turned Off through PMBus control, the ON-OFF pin control function will be
ignored.
Various ON-OFF pin connection schemes are shown below:
PMBus Interface
AC(L)
AC(N)
PFH500F
Case
Inrush
-VBUS
Control
Fig. 6-7a ON-OFF Pin Tied Active.
NOTE: Module is always On
6.10 Power Good Signal (PGood)
PFH Series modules have an Open-Drain Power Good pin. The PGood pin can be used to either turn on or off load(s), or to
communicate with external controllers and signal the system regarding the status of PFH module. An external pull-up
resistor is required to limit sink current.
When the output voltage of PFH module is within the specified output voltage regulation band, the Power Good signal is
activated. An active "Low level" indicates Power Good.
Maximum sink current of Power Good pin
Maximum voltage of Power Good Pin
V
(Max)
OUT_LOW
Some filtering (hardware and/or software) of the Power Good pin may be required for applications with large noise levels.
REV 2.8 (March 30, 2020)
RS (+)
Vo(+)
+
Vo(+)
Vout
Load
C15
C16
Vo(-)
-
Vo(-)
Trim
PG
ON/OFF
Aux Power
SGND
+ VBUS
:
300µA
:
1V
:
3.3V
Fig. 6-7b ON-OFF Control Using Switch.
NOTE: S1 should be located next to the module
:
150mA
:
50V
:
1V @ 150mA
TDK-Lambda
PFH500-SERIES
INSTRUCTION MANUAL
20
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