Hex/Quad, Power-Supply Supervisory Circuits

8

_______________________________________________________________________________________

detector input (IN1–IN6) to monitor a user-defined sup-

ply voltage:

Use the following procedure to design the proper volt-

age-divider and calculate thresholds:

1) Pick a value for R2. Use the equation above with

the desired supply voltage to be monitored and

solve for R1. Use high-value resistors R1 and R2 to

minimize current consumption due to low leakage

currents.

2) To find the actual undervoltage and overvoltage

thresholds, use the following equations:

age thresholds listed in Tables 1 and 2 that allow

adjustable thresholds. Their values are based on toler-

ances of ±7.5% and ±12.5% from a 0.6V reference.

See the

Selector Guide to find which thresholds in

Tables 1 and 2 are adjustable.

Manual Reset (

MR)

Many µP-based products require manual reset capability

to allow an operator or external logic circuitry to initiate a

reset. The manual reset input (MR) can be connected

directly to a switch without an external pullup resistor or

debouncing network. MR is internally pulled up to BP.

Leave unconnected if not used. MR is internally pulled

up to BP through a 10µA current source. MR is designed

to reject fast, falling transients (typically 100ns pulses)

and MR must be held low for a minimum of 1µs to assert

RESET. Connect a 0.1µF capacitor from MR to ground to

provide additional noise immunity. After MR transitions

from low to high, RESET remains asserted for the dura-

tion of its time delay.

Margin Output Disable (

MARGIN)

MARGIN allows system-level testing while power sup-

plies exceed the normal operating ranges. Drive

MARGIN low to hold RESET, OV, and WDO in their

VV

V

V

VV

V

V

ACTUALUV

MON

REFUV

ACTUALOV

MON

REFOV

=× ⎛

⎝⎜

⎞

⎠⎟

=× ⎛

⎝⎜

⎞

⎠⎟

06

06

.

.

06

2

12

.V

V

R

RR

MON

=×

+

⎛

⎝⎜

⎞

⎠⎟

Table 1. MAX6887 Threshold Options

UV THRESHOLDS (V)

OV THRESHOLDS (V)

PART

IN1

IN2

IN3

IN4

IN5

IN6

IN1

IN2

IN3

IN4

IN5

IN6

MAX6887AETE

4.620

3.060

2.310

1.670

0.557

0.557

5.360

3.540

2.680

1.930

0.643

0.643

MAX6887BETE

4.620

3.060

2.310

0.557

0.557

0.557

5.360

3.540

2.680

0.643

0.643

0.643

MAX6887CETE

4.620

3.060

1.670

0.557

0.557

0.557

5.360

3.540

1.930

0.643

0.643

0.643

MAX6887DETE

3.060

2.310

1.670

1.390

0.557

0.557

3.540

2.680

1.930

1.610

0.643

0.643

MAX6887EETE

3.060

2.310

1.670

0.557

0.557

0.557

3.540

2.680

1.930

0.643

0.643

0.643

MAX6887FETE

3.060

2.310

1.390

0.557

0.557

0.557

3.540

2.680

1.610

0.643

0.643

0.643

MAX6887GETE

3.060

2.310

0.557

0.557

0.557

0.557

3.540

2.680

0.643

0.643

0.643

0.643

MAX6887HETE

3.060

1.670

0.557

0.557

0.557

0.557

3.540

1.930

0.643

0.643

0.643

0.643

MAX6887QETE

0.557

0.557

0.557

0.557

0.557

0.557

0.643

0.643

0.643

0.643

0.643

0.643

MAX6887IETE

4.380

2.880

2.190

1.580

0.527

0.527

5.620

3.700

2.810

2.020

0.673

0.673

MAX6887JETE

4.380

2.880

2.190

0.527

0.557

0.557

5.620

3.700

2.810

0.673

0.673

0.673

MAX6887KETE

4.380

2.880

1.580

0.527

0.557

0.557

5.620

3.700

2.020

0.673

0.673

0.673

MAX6887LETE

2.880

2.190

1.580

1.310

0.557

0.557

3.700

2.810

2.020

1.680

0.673

0.673

MAX6887METE

2.880

2.190

1.580

0.527

0.557

0.557

3.700

2.810

2.020

0.673

0.673

0.673

MAX6887NETE

2.880

2.190

1.310

0.527

0.557

0.557

3.700

2.810

1.680

0.673

0.673

0.673

MAX6887OETE

2.880

2.190

0.527

0.527

0.557

0.557

3.700

2.810

0.673

0.673

0.673

0.673

MAX6887PETE

2.880

1.580

0.527

0.527

0.557

0.557

3.700

2.020

0.673

0.673

0.673

0.673

MAX6887RETE

0.527

0.527

0.527

0.527

0.527

0.527

0.673

0.673

0.673

0.673

0.673

0.673