Equinox Systems GEMINI Guide de l'utilisateur télécharger pdf (Page 39)

User Guide V1.10

Programmer Power Supply Requirements

The programmer draws its power from the target system. To ensure that the programmer

operates reliably, it is imperative that the target power supply meets the voltage and current

requirements of the programmer shown in the ‘Systems Specifications’ section of the manual.

When programming target devices which require a +12Vpp, care should be taken to ensure

that the target power supply can cope with the inrush current as the Gemini ‘Vpp Generator

Circuit’ switches on.

Failure to meet these requirement may result in erratic programmer

operation as the programmer will automatically reset itself when an unstable supply is detected.

Power supply design notes:

The suggested circuit shown in figure 26 is capable of reliably supplying +5V to both the target

and the programmer. The capacitors C1,C2,C3,C4 shown must be fitted to ensure that the

regulator does not oscillate. Failure to fit these components can result in spurious oscillations of

the ‘Target Vcc’ supply which can cause the programmer to automatically reset itself. The diode

D1 protects against accidental reverse polarity of the external power supply. The diode D2

protects the regulator in the event of the target system trying to discharge back towards the

power supply input.

Important Note

i Please check that the specification of your target power supply meets the required specification

for the programmer. If you encounter erratic operation of the programmer, please use an

oscilloscope to check that the ‘Target Vcc’ is within limits and that there are no glitches on the

supply. Also, check that the Vcc ripple and noise are within acceptable limits.

ii If you are using the Philips ‘P89C51Rx+ ISP Target Board’ with this programmer, please ensure

that you add capacitors C1 and C2 to the board. Without these components, the target Vcc

oscillates and causes the programmer to continuously reset.

Target System - ISP Design Requirements continued

Figure 26

Target Vcc

Target GND

COMMON

VIN

VOUT

External PSU

9V - 25V DC

Regulated

C3 47nF Polyester

C4 100nF Polyester

D1 Diode e.g. IN4002

D2 Diode e.g. IN4002

Suggested +5V Target Power Supply

REG1

KEY

REG1 7805

PSU1 Regulated Power Supply 9V-25V DC

C1 100µF 35V Electrolytic

C2 47nF Polyester

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 57 58

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Equinox Systems GEMINI Guide de l'utilisateur Page 39

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