Applications Information

Tolerance

The MAX16025–MAX16030 feature a pin-selectable

threshold tolerance. Connect TOL to GND to select the

thresholds 5% below the nominal value. Connect TOL to

nominal voltage. Do not leave TOL unconnected.

Adjustable Input

These devices offer several monitoring options with

both fixed and/or adjustable reset thresholds (see

Table 2). For the adjustable threshold inputs, the

work to the circuit as shown in Figure 3 and use the fol-

lowing equation to calculate the threshold voltage:

Choosing the proper external resistors is a balance

between accuracy and power use. The input to the volt-

age monitor is a high-impedance input with a small

100nA leakage current. This leakage current con-

tributes to the overall error of the threshold voltage

where the output is asserted. This induced error is pro-

portional to the value of the resistors used to set the

threshold. With lower value resistors, this error is

reduced, but the amount of power consumed in the

resistors increases.

The following equation is provided to help estimate the

value of the resistors based on the amount of accept-

able error:

absolute resistive divider error attributable to the input

the worst-case IN_ leakage current (see the

Electrical

Characteristics). Calculate R2 as follows:

Unused Inputs

OUT_ Output

An OUT_ goes low when its respective IN_ input voltage

drops below its specified threshold or when its EN_ goes

low (see Table 1). OUT_ goes high when EN_ is high and

MAX16025/MAX16027/MAX16029 feature open-drain,

outputs while the MAX16026/MAX16028/MAX16030

have push-pull outputs. Open-drain outputs require an

external pullup resistor to any voltage from 0 to 28V.

RESET Output

RESET asserts low when any of the monitored voltages

(IN_) falls below its respective threshold, any EN_ goes

low, or

MR is asserted. RESET remains asserted for the

reset timeout period after all of the monitored voltages

exceed their respective threshold, all EN_ are high, all

OUT_ are high, and

MR is deasserted. The MAX16025/

MAX16027/MAX16029 have an open-drain, active-low

reset output, while the MAX16026/MAX16028/

MAX16030 have a push-pull, active-low reset output.

Open-drain

RESET requires an external pullup resistor to

any voltage from 0 to 28V.

Adjustable Reset Timeout Period

(CRESET)

All of these parts offer an internally fixed reset timeout

timeout can also be adjusted by connecting a capaci-

tor from CRESET to GND. When the voltage at CRESET

reaches 0.5V,

RESET goes high. When RESET goes

high, CRESET is immediately held low.

R

VR

VV

TH

INTH

TH

2

1

=

×

−

R

eV

I

A

INTH

L

×

VV

R

R

INTH

TH

=× +

⎛

⎝⎜

⎞

⎠⎟

1

1

2

Dual-/Triple-/Quad-Voltage, Capacitor-

Adjustable, Sequencing/Supervisory Circuits

10

______________________________________________________________________________________

IN_

R1 = R2 x

(

)

R1

R2

MAX16025–

MAX16030

-1

Figure 3. Setting the Adjustable Input