Installation and Operation
©
2009 Microchip Technology Inc.
DS51811A-page 11
2.3.4
Power Good (PWRGD)
The Power Good (PWRGD) output pin has the ability to be pulled up to either SHDN
or V
OUT
. Populating R2 (and removing R4) with the desired pull-up resistor causes
PWRGD to be pulled up to V
OUT
. Populating R4 (and removing R2) with the desired
pull-up resistor causes PWRGD to be pulled up to V
IN
.
When PWRGD is pulled up to V
OUT
, the device current will be minimal when SHDN is
active. When PWRGD is pulled up to V
IN
, the device current will be higher when when
SHDN is active because the current will flow threw R4 and the PWRGD pin to ground.
When low operating currents are critical, PWRGD should be pulled up to V
OUT
. That
will keep current consumption at a minimum when SHDN is active because the output
voltage will be low.
2.3.5
Load Resistance
R5 is used to set the desired load value. Jumper JP4 is used to connect or disconnect
the load resistance to the output.
2.3.6
Line Step
Dynamic Line Step response may be evaluated by connecting an electronically
switched input voltage to testpoints TP1(+) and TP2(-) or to connector J1. An
oscilloscope is connected to TP3 (Ch1 Trigger), TP9 (Ch2) and TP10 (GND). An
appropriate load is selected using R5 and JP4. The input voltage is then electronically
switched from a low voltage to a high voltage. The corresponding voltage waveform
data of the voltage regulator response is captured by the oscilloscope. Microchip will
be offering a Line Step module that connects directly to connector J1. The Line Step
module will be capable of switching between two voltage levels that the user supplies
2.3.7
Load Step
Dynamic Load Step response may be evaluated by connecting an electronically
switched load to testpoints TP9(+) and TP10(-) or to connector P1. An oscilloscope is
connected to the electronic load switch signal (Ch1 Trigger) and to TP9(Ch2) and
TP10(GND). The load is then electronically switched from a high resistance to a low
resistance. The corresponding voltage waveform data of the voltage regulator
response is captured by the oscilloscope. Microchip will be offering a Load Step module
that connects directly to connector P1. The Load Step module will have several
selectable load values populated onboard to cover a wide range of loads. The load will
have the ability to be electronically or manually switched.
2.3.8
Power Supply Rejection Ratio (PSRR)
Power Supply Rejection Ratio tests are performed by removing the input capacitor
jumper, JP1, and connecting an appropriate PSRR analyzer to the SOT23-5 Voltage
Regulator Evaluation Board. The PSRR analyzer may then sweep the input voltage
frequencies and record the corresponding output voltages.
