eight Darlington PNPTransistors

[chandu13]

Hi

Presently iam using 18 PIN ULN2803 eight Darlington NPN Transistors IC.

Now I want replace this IC with 18 PIN eight Darlington PNPTransistors on the PCB.

Please suggest me 18 PIN eight Darlington PNPTransistors IC or its equal lent IC which Is sutable for my PCB

Regards
chandu

 

[Gayan Soyza]

Use UDN2982A source driver IC but its expensive than ULN2803.

 

[chandu13]

active low input

Thanks for reply

UDN2982A well activated by an active high input.

I required active low input

please suggest me active low input Transister Darlington arrays

or Source Drivers.

my apllication is controlling the Motars and Pumps using 89C51

Regards

chandu

 

[Gayan Soyza]

Thanks for reply

UDN2982A well activated by an active high input.

I required active low input

please suggest me active low input Transister Darlington arrays

or Source Drivers.

my apllication is controlling the Motars and Pumps using 89C51

Regards

chandu

You invert your code & give inputs to the darlington arrays.

 

[Mike - K8LH]

No, no, no Goyan. The two devices are entirely different. The '2803 is a "sinking" driver and the '2982 is a "sourcing" driver.

 

[justDIY]

No, no, no Goyan. The two devices are entirely different. The '2803 is a "sinking" driver and the '2982 is a "sourcing" driver.

that is what the OP asked for, a pnp array. better question is, where can someone even find the 2982

chandu, you could use a 74HC540 inverting line driver if you don't want to flip the bits in your software.

 

[Mike - K8LH]

My mistake. Oops!

 

[chandu13]

Reset problem

hi

In my project iam using 89c51 and ULN2803 (no inverter in between89c51 and 2803) When I press reset button all 89c51 ports are high, 2803 will work with active high signal ,In this moment my all relays are ON for some milliseconds, ofter that iam making all ports are low. Due to the reset time iam facing the problem. My PCB is already made, so I don’t want change the PCB again with inverter IC

For My problem I have two solutions

1. I want use PNP transistor array witch is equal lent PIN configuration to the ULN 2803

2. I required INVERTER device features inputs and outputs on opposite sides of the package. I well bend ULN2803 Pins for 90 degrees and I well place this IC on the IC base one end, I well solder the inverter IC which comparable with ULN 2803 on the second side.

Please suggest me Inverter IC which inputs and outputs on opposite sides and PNP transistor array IC

Thanks

Regards

chandu

 

[justDIY]

the inverter ic mentioned already has inputs on one side and outputs on the other - the datasheet even brags about it as a feature to ease board design.

however, I don't think you'll be able to just 'swap' a low side driver for a high side driver, their polarities are different. if your pcb was originally designed around the low side driver 2803, then the relay coils are already tied high and the driver completes the circuit, pulling the other side of the coil low.

ok, lets back up...

the problem is, when you hold your micro controller in reset, all it's outputs go high, and then turns on all your relays, which you don't want?

what you need is a 'bus driver' with an active-low output enable pin.

The 74HC541 should work for you, if you can figure out how to squeeze it onto your board. it is the non inverting version of the 74HC540 and has two active-low "enable" pins... when the enable pin is driven high, the outputs are floating tristate. when enable is driven low, by your uC after it boots up, the outputs become equivalent to the inputs (high/low)

as for fitting it onto your board, how about making a daughter board that will plug into the socket for the 2803. the daughter board will carry the '540 and the 2803. your idea of bending the pins should work too, plug the '540 into the input side of the socket and the 2803 into the output side, and solder the rest of the pins to each other

 

[Mike - K8LH]

I'd suggest he needs nothing more complex than a single "pull down" resistor network in a SIP package (grin)...

 

[justDIY]

awe, where is the fun in that!

 

[blueroomelectronics]

I'd suggest he needs nothing more complex than a single "pull down" resistor network in a SIP package (grin)...

The ULN2803 has 10K pulldowns. Doesn't seem to help.

 

[Mike - K8LH]

You might want to check the data sheet again. There's a 2K7 resistor on the input before the 10K internal pull-down.

 

[justDIY]

what's the datasheet for the UC say about the reset condition of its output pins? maybe they are driven high, in which case a pulldown wouldn't help anyway.

 

[blueroomelectronics]

You might want to check the data sheet again. There's a 2K7 resistor on the input before the 10K internal pull-down.

Well it's still a pulldown, the 2803 with nothing on the inputs will power up in a known off state, the problem appears to be the way the 8051 powers up its I/O.

 

[chandu13]

74hc540

Hi

Now iam planning to use 89C51+74HC540+ULN2803.

74HC540 Is equal lent to inverter IC(74HC04) ?

Can I use 74HC540 in between 89C51 and ULN2803


Regards

chandu

 

[ahmedragia21]

i've faced this problem before , well try to make all the ports 0xFF before going to the main loop ....