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MAX038CPP Folha de dados(PDF) 2 Page - Maxim Integrated Products |
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MAX038CPP Folha de dados(HTML) 2 Page - Maxim Integrated Products |
2 / 8 page JU3 to allow the frequency to be adjusted. Verify that there is a shunt on JU5. 4) Verify the shunts on JU1 and JU2 for a square-wave output. Refer to Table 1 for alternate waveform selections. 5) Apply power and verify the output waveform. _______________Detailed Description Waveform Selection To select the desired output waveform, place shunts across JU1 and JU2 in the combinations shown in Table 1. These jumpers set address pins A0 and A1 to TTL/CMOS-logic levels. External control may be initiat- ed by connecting an external source to the A0 and A1 pads and removing the shunts on JU1 and JU2. Note that there are 10k Ω pull-up resistors to +5V on the A0 and A1 address lines. * Note: Frequency pre-set by oscillator capacitor (C1) and input current (position of R3) as specified by formula [1]. Output Frequency The output frequency is controlled by the oscillator capacitor (C1), the current injected into the IIN pin, and the voltage on the FADJ pin. The EV kit allows indepen- dent adjustment of both input current (R3) and FADJ voltage (R2). Refer to the Detailed Description section of the MAX038 data sheet for additional theory of oper- ation. Input Current Control The current injected into the IIN pin acts as the primary frequency-adjustment control. The R3 potentiometer varies the current to the MAX038’s IIN pin. The input current can be easily monitored by removing the JU5 shunt and placing a current meter across the JU5 pins. The components supplied on the EV kit will allow an input current range of 50µA to 725µA. With the VADJ pin grounded, the fundamental output frequency (Fo) is as follows: Fo (MHz) = IIN(µA) ÷ COSC (pF) [1] where: IIN = current injected into IIN = VREF ÷ (R3 + R12) = 2.5V ÷ (0kΩ to 50kΩ + 3.3kΩ) COSC = external oscillator capacitor (C1) To use an external input current, connect the external current source to the IIN pad and remove the JU5 shunt completely. Note that there is a 3.3k Ω resistor in series with the device IIN pin. FADJ Control Varying the FADJ voltage will also vary the output fre- quency. With a shunt across pins 1 and 2 of JU3, the R2 potentiometer will vary the voltage applied to the FADJ pin. With the JU3 shunt on pins 2 and 3, the FADJ pin is grounded. Grounding the FADJ pin sets the out- put to the fundamental output frequency (Fo), as given by equation [1]. To use an external FADJ voltage, connect the external source to the FADJ pad and remove the JU3 shunt completely. Limit the external FADJ voltage to ±2.4V. Duty-Cycle Control The voltage on the DADJ pin controls the duty cycle of the output waveform. With the JU4 shunt on pins 1 and 2, the R1 potentiometer will vary the voltage applied to the DADJ pin, thus varying the duty cycle 15% to 85%. With the JU4 shunt on pins 2 and 3, the DADJ pin is grounded. Grounding the DADJ pin fixes the duty cycle at 50%. To use an external DADJ voltage, connect the external voltage source to the DADJ pad and remove the JU4 shunt completely. Limit the external DADJ voltage to ±2.3V. MAX038 Evaluation Kit 2 _______________________________________________________________________________________ Table 1. Waveform Jumper Select Table 2. Frequency and Duty-Cycle Jumper Select Fixed 50% Duty Cycle 2 & 3 JU4 Adjustable Duty Cycle 1 & 2 Pre-Set Frequency* 2 & 3 JU3 Adjustable Frequency 1 & 2 MAX038 OUTPUT SHUNT LOCATION JUMPER Square Wave Short Short Triangle Wave Short Open Sine Wave Open Don't Care OUTPUT WAVEFORM JU2 JU1 |
Nº de peça semelhante - MAX038CPP |
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Descrição semelhante - MAX038CPP |
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