Tech Brief No. 13 Modifying the DS1075K Board to Work With the DS1073 3.6 V EconOscillator Bob Brown, Product Manager, EconOscillators |
The original DS1075K Development Kits[1075k.pdf - MISSING] were designed to work with 5 V devices (e.g., the DS1075 and DS1065 EconOscillators). With the advent of the 3-volt DS1073 came the need to be able to program 3-volt devices with the DS1075K. The DS1075K (Rev C) has been re-designed to allow for 3-volt operation. These Rev C boards can be identified by a sticker on the box sleeve and a voltage select jumper installed on the board. This article shows a method to modify older DS1075Ks to work with the newer 3-volt devices. The main requirement of the modification is to supply 3 volts to the DS1073 3-Volt EconOscillator to be programmed while preserving the 5-volt supply needed by the remainder of the components on the board. Furthermore, the 3 volts must be able to be cycled by the board to enter/exit from the program mode of the device. NOTE: It is quite possible to program the DS1073 without damaging the device on an unmodified DS1075K. However, the measured output frequency from the board will be quite inaccurate as the DS1073 is being operated outside its specified voltage range. Modification Procedure Figure 1: Modifications to the back of the DS1075K PCBStep 2. Q1 must be replaced by a pnp transistor, e.g., 2N2907. In addition, the PCB gate trace which was originally used to drive the Q1 gate must be cut and a 220 Ohm R7 series resistor inserted to limit the base current of Q1. The trace is accessible from the back of Q1 on the PCB. This is also a convenient location to add the resistor. The photo below shows the placement and result of the modifications. Figure 2: DS1075 PCB after modificationUsing the DS1075K to Program 5-volt and 3-volt EconOscillators DS1065 and DS1075 EconOscillators DS1073 EconOscillator NOTE: The voltage should be measured at the DS1073 supply pin to prevent errors caused by the voltage drop across Q1. |