APPENDIX E Receiver Card Interface Examples
OEM7 Installation and Operation User Manual v4
216
E.2 Position Valid (PV) LED Driver
The PV signal may be used to indicate that the receiver card has computed a valid position.
Many NovAtel enclosure products use it to drive a green LED on the enclosure. It may also be
used to monitor the status of the receiver with an external microcontroller.
If the LED requires less than 6 mA to drive, and can be operated from a 3.3 V supply, the PV pin
may be used to drive the LED directly (with an appropriate current-limiting resistor). If the LED
must be driven from a different supply voltage or requires more than 6 mA, a buffer must be
used.
A simple buffer – suitable for driving a high-brightness LED from a 5 V supply – is shown below.
The value for R2 was selected to limit the LED current to 10 mA (assuming V
CE(Q1,sat)
=0.25 V,
V
FWD(D1)
=3.4 V). This circuit will not compensate for the forward voltage change over tem-
perature (and the resulting brightness changes).
Figure 59: OEM7 Buffer for Driving High-Brightness LEDs from PV
OEM719
OEM729
OEM7700
OEM7720
Connector
P1701
P1802
P2001
P1901
PV
17
10
22
22
Table 48: PV Pin Designation
Designator
Manufacturer
Manufacturer Part Number
Q1
ON Semiconductor
Fairchild Semiconductor
Diodes Inc
MMBTA06LT3G
MMBTA06LT1G
MMBTA06-7-F
D1
OSRAM
LT L29S-N1R2-25-Z
Table 49: PV LED Driver Bill of Materials (critical components)
