Electrical changes
COM Port Data Rate
The maximum data rate for COM ports has changed. On OEM6 receivers, the maximum data rate was 921,600 bps. On OEM7 receivers, the maximum data rate is 460,800 bps.
Power Supply
The power consumption of OEM7 receivers is dependent on receiver configuration and feature use. Enabling more features (e.g. interference detection) will increase the power required.
-
The OEM719 power consumption is approximately 10% higher than a similarly configured OEM615.
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The OEM729 power consumption is approximately 10% lower than a similarly configured OEM628.
A monotonic rise of the supply voltage input is required to guarantee a proper power-on reset sequence. The maximum rise time is 100 ms.
Bulk supply bypassing (approx 10 µF) and high-frequency bypassing (0.1 µF and 220 pF) near the supply pin is recommended for optimal performance.
On the OEM7 receiver cards, there is an approximate effective input bulk capacitance of 100 µF at room temperature. This is made up of ceramic capacitors with a voltage rating of 6.3 VDC and tolerance of 20%.
OEM7 receivers monitor the supply voltage. If the supply voltage falls outside of the normal operating range, a warning or error is provided in the RXSTATUS log. See the RXSTATUS log for more information.
Inrush Current
The inrush current behavior of the OEM7 receivers is different than the OEM6 receivers.
|
OEM6 Receiver |
Inrush Current (Typical) |
|---|---|
|
OEM615 |
6.0 A for less than 60 µs |
|
OEM617 |
6.0 A for less than 60 µs |
|
OEM617D |
6.0 A for less than 60 µs |
|
OEM628 |
6.6 A for less than 60 µs |
|
OEM638 |
12.0 A for less than 60 µs |
|
OEM7 Receiver |
Inrush Current (Typical) |
|---|---|
|
OEM719 |
1.71 A for less than 1.5 ms |
|
OEM729 |
2.0 A for less than 1.8 ms |
|
OEM7500 |
1.7 A for less than 1.5 ms (3.3 VDC) No inrush current for 1.2 VDC |
|
OEM7600 |
2.0 A for less than 1.8 ms |
|
OEM7700 |
2.0 A for less than 1.8 ms |
|
OEM7720 |
2.0 A for less than 1.8 ms |
USB Interfaces
The layout guidelines are identical to those provided for OEM6, but the recommended common-mode choke value has changed. See USB Interface.
The OEM719 and OEM729 USB interfaces operate at 12 Mb/s ("Full-Speed") operation for backwards-compatibility reasons.
Input and Output lines
The voltage limits and drive currents on the input and output lines of the OEM7 receivers are different than the levels on the OEM6 receivers. See Table: OEM719 Strobe Electrical Specification and Table: OEM729 Strobe Electrical Specifications for details.
LNA Power
If a short circuit or other problem causes an overload of the current supplied to the antenna, the receiver hardware shuts down the power supplied to the antenna. To restore power, power cycle the receiver. The Receiver Status word, available in the RXSTATUS log, provides more information about the cause of the problem.
OEM719
On OEM615 receivers, LNA power is provided by an external power supply connected to pin 1 of the main connector.
On OEM719 receivers, LNA power is generated on the receiver and pin 1 of the main connector has no electrical connection on the board. The OEM719 provides up to 200 mA of current at +5 VDC. The LNA is generated from the 3.3 V supply; therefore the OEM719 will draw more power on the 3.3 V rail than a similarly configured OEM615.
The typical current draw for a NovAtel active antenna is <40 mA. For a typical antenna, this may increase the power drawn from the 3.3 V supply by as much as 70 mA (as the LNA supply is approximately 85-90% efficient).
OEM729
On OEM628 receivers, the voltage provided to the LNA could be changed from the default of +5 VDC to +3.3 VDC using the ANTENNAPOWER command.
The voltage for the LNA power is not selectable on OEM729 receivers, but the OEM729 can provide more current to the LNA. The OEM729 provides up to 200 mA of current at +5 VDC.