DRIVE50

50 Ohm Driver Card

• "TTL" Level Line driver
• 50 or 75 Ohm output impedance
• BNC or SMA output connector
• 10K pull-up on input
• Card is non-inverting
• 1.5V-5.5V power
  • Typically 3.3V or 5V
• 3-pin right angle 0.1" pitch input connector
• (4) 4-40 mounting holes

Driver

• 5x paralleled 74AC14 drivers
  • 24mA per pin max current output
    • Symmetric high-low drive levels
  • Short-circuit proof
    • 5V, 250 Ohms to ground is 20 mA (pins are rated for 24 mA)
    • 0.125 W resistor (5V output through 249 ohm resistor with output shorted to ground is 0.1 W)
    • 3.3V, 250 Ohms to ground is 13.2 mA (pins are rated for 24 mA)
    • 0.125 W resistor (3.3V output through 249 ohm resistor with output shorted to ground is 0.044 W)
• Card has input buffer stage
• Schmitt Trigger Input
• 3.3V, 250 Ohm resistors (/5) for 50 Ohm output
  • Normal output = 10 mA per pin

Test

• Manual or Automated test methods

Manual Test Method

• Supply Vcc 3.3V to 5V and ground
• Input is pulled up to Vcc
• Measure output with BNC T
  • Should be 1/2 of Vcc with 50 Ohm terminator
  • Should be Vcc without terminator

Automated Test Software Method

Setup

• QTPy49 or QTPy49-01 card
• QT Py (RP2040_based) card
  • Analog cable
  • GVS Cable to A1
  • Analog in (BNC) to A0 on QTPy49
• MyMenu card
• Power card options
  • Connect USB-C to the QT Py (RP2040 based) or
  • Power from 9-12V to DC jack
• Terminator - dependent on build option
  • 50 Ohms
  • 75 Ohms
• Unit Under Test (UUT)
• PulseGen_DRIVE50_Test.py
  • Test software for PulseGen and DRIVE50 cards
    • Auto-detects card type
  • Stored as code.py on QT Py (RP2040 based) to auto-run

Procedure

• Connect 3 pin power cable to card
• Connect BNC T to output of card
• Connect BNC female from tester to BNC T male
• Install 50 terminator to other side of BNC T
• Connect USB C cable
• Display will show

PulseGen/DRIVE50 V1.1
50 Ohm card
Set/Got Low
Term High = OK

• All 3 LEDs are on

Application Example

GPS Frequency Standard

• GPS Frequency Standard
• Card takes in PPS signal out of GPS module and drives 50 Ohm, 10 MHz Frequency Standard output on coax via BNC connector

Mechanicals

Assembly Sheet

• DRIVE50 Assembly Sheet