PIC16F88 Current Consuption in Sleep mode

eleqtc · Joined: 20 Jan 2004 Posts: 5

Hi,

Have a PIC16F88 in a 72mS WDT sleep loop, A/D disabled, Timer1 disabled, INT_RC osc at 2MHz, Port A set to O/P all at low state with no external connections except for RA3 A/D i/p (set to i/p) tied low via resistor. Port B set to output and high state with no connections to external devices. I'm reading 70uA operating current with 3 volt operation. WDT only takes a few uA according to datasheet so can I get it lower than 70uA ? What's taking all these microamps?

Thanks,
Tony

Just tried osc set to 1MHz , current down to 63uA. Still not good enough.
It would suggest something is enabled ..........somewhere

Neutone · Joined: 08 Sep 2003 Posts: 839 Location: Houston

And how much current while the WDT is disabled and it is in sleep mode?

Guest · Posted: Wed Jan 21, 2004 1:23 pm

Post your #fuses statement, and also post all peripherals that you use.
(I want to see if you have Brownout enabled, or the comparator,
or Vref, etc.) With regard to external connections, what circuit do
you have on the MCLR pin ?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

That post above was from me. Somehow, I got logged in as Guest.
I fixed that.

Guest · Posted: Wed Jan 21, 2004 3:05 pm

How bizzare. The reason I'm trying to get a lower consumption is that I got about 17uA with a PIC16LF84 in sleep mode.

// compiled with PCWH version 3.180

#include <16F88.H>
#fuses MCLR, NOBROWNOUT, NOLVP, WDT, NOCPD, NOPROTECT, INTRC_IO, PUT, NODEBUG
#device adc=8
#use fast_io(A)
#use fast_io(B)
#use delay(clock=2000000)

// rem'd out these two lines, no change.
#use rs232(baud=9600, rcv=PIN_B2,xmit=PIN_B5, parity=N, bits=8, errors, restart_wdt )
#use I2C(master, sda=PIN_B1, scl=PIN_B4, fast)

#byte adcon0 = 0x1f

/* As you can see I'm using RS232 and I2C but have commented out any such routines to try to
see what's going on. This is the only code compiled.

*/

main() {

setup_oscillator(OSC_2MHZ | OSC_INTRC);

disable_interrupts(GLOBAL);

setup_wdt(WDT_72MS) ;

set_tris_a(0x00); // RA4 for A/D input
porta = 0x00 ;

set_tris_b(0x00) ;
portb = 0xff ;

// Nothing physically connected to any port pins

adcon0 = 0x20 ; // turn adc off

port_b_pullups(true); // true or false, no difference to current consuption
setup_timer_1 ( T1_DISABLED );

while(true) {
// no difference with or without these two lines.
output_low(CS_DIGPOT); // like to see a pulse to measure actual WDT time.

//delay_ms(1); // did have this in to see pulse better on oscilloscope

output_high(CS_DIGPOT);
sleep();

} // end while loop

} // end main

eleqtc · Joined: 20 Jan 2004 Posts: 5

Yes I managed to post my code as Guest.
I forgot the reset circuit. It's the standard R-C as per the datasheet.

Tony

eleqtc · Joined: 20 Jan 2004 Posts: 5

It's the internal oscillator. Clock switching now gives me 3.4uA if I don't wait for a stable oscillator. That matches the datasheet info for the WDT with my 3 volt supply.

If I do wait as in the code below I have to wait just over 4mS for stability with an average current of 16uA drawn.

I wish it only took me 4mS to wake up properly each morning !

Regards,
Tony

while(true) {

setup_oscillator(OSC_31kHZ | OSC_INTRC);
sleep();
setup_oscillator(OSC_2MHZ | OSC_INTRC);

output_low(pin_b3); // see time overhead
IOFS=false;
while(!IOFS) {}
output_high(pin_b3);

}