©
National Instruments Corporation
13
NI USB-622x/625x OEM User Guide
Power Switch
The power switch on the USB-622
x
/625
x
OEM device powers the device
on and off. Figure 11 shows the pins on the power switch and circuitry.
Figure 11.
Schematic for the Power Switch
Pin 1, VDC In, is connected to VDC through the fuse (reference designator
XF1). The VDC is the voltage provided by the power supply through the
power connector (reference designator J4/J6/J8
1
) and must be 11–30 VDC,
20 W.
Pin 2, VDC Out, provides power to the circuitry on the device. When the
switch is in the On position, the VDC power supply from pin 1 is routed to
pin 2.
Pin 3, 100 k
Ω
to Ground, connects pin 2 to ground through a 100 k
Ω
resistor when the switch is in the Off position.
1
The power connector is designated as J4 on USB-6225/6255 OEM devices, J6 on USB-6221/6229 OEM devices, and J8 on
USB-6251/6259 OEM devices.
J4/J6/J8
VDC Out
VDC In
XF1
Switch
1
2
3
NC
NC
100 k
Ω
SW1
Outer
Shell
SW1
XF1
FUSE
3
Power to
Device
J4/J6/J8
Power
Connector
1
2
100 k
Ω
100 k
Ω
to Ground
