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 VCE(Q1,sat)=0.25 V, VFWD(D1)=3.4 V). This circuit will not compensate for the forward voltage change over temperature (and the resulting brightness changes).

OEM7 buffer for driving high-brightness LEDs from PV

PV pin designation

 

OEM719

OEM729

OEM7600

OEM7700

OEM7720

Connector

P1701

P1802

P1701

P2001

P1901

PV

17

10

22

22

22
PV LED driver bill of materials (critical components)

Designator

Manufacturer

Manufacturer part number

Q1

ON Semiconductor

Fairchild Semiconductor

Diodes Inc

MMBTA06LT3G

MMBTA06LT1G

MMBTA06-7-F

D1

OSRAM

LT L29S-N1R2-25-Z