Low-Voltage, High-Accuracy, Quad Window

Voltage Detectors in Thin QFN

_______________________________________________________________________________________

9

Detailed Description

The MAX16008/MAX16009 are adjustable quad win-

dow voltage detectors in a small thin QFN package.

These devices are designed to provide a higher level of

system reliability by monitoring multiple supply voltages

and providing a fault signal when any of the voltages

exceeds its overvoltage threshold or falls below its

undervoltage threshold.

These devices offer user-adjustable thresholds that

allow voltages to be monitored down to 0.4V. The

devices allow the upper and lower trip thresholds of

each window detector to be set externally with the use

of three external resistors.

Each monitored threshold has an independent open-

drain output for signaling a fault condition. The outputs

can be wire OR’ed together to provide a single fault

output. The open-drain outputs are internally pulled up

with a 30µA current, but can be externally driven to

other voltage levels for interfacing to other logic levels.

Both devices feature a margin input to disable the out-

puts during margin testing or any other time after

power-up operations. The MAX16009 offers a reset out-

put that deasserts after a reset timeout period after all

voltages are within their threshold specification. The

reset timeout is internally set to 140ms (min), but can

be externally adjusted to other reset timeouts using an

external capacitor. In addition, the MAX16009 offers a

manual reset input.

Applications Information

Voltage Monitoring

The MAX16008/MAX16009 feature undervoltage and

overvoltage comparators for window detection (see

Figure 2). UVOUT_/OVOUT_ deassert high when the

monitored voltage is within the “selected window.”

When the monitored voltage falls below the lower limit

the monitored voltage exceeds the upper limit

Figure 2 shows the MAX16008/MAX16009 enabling the

DC-DC converter when the monitored voltage is in the

selected window.

The resistor values R1, R2, and R3 can be calculated

as shown:

Use the following steps to determine the values for R1,

R2, and R3:

R3. Because the MAX16008/MAX16009 have very

to 2M

Ω. Large-value resistors help minimize power

consumption. Lower-value resistors can be used to

maintain overall accuracy.

VV

R

RR

VV

R

R

TRIPLOW

TH

TOTAL

TRIPHIGH

TH

TOTAL

=

+

⎛

⎝⎜

⎞

⎠⎟

=

⎛

⎝⎜

⎞

⎠⎟

23

3

+5V

IN

GND

UVIN_

OVIN_

EN

OUT

R1

R2

R3

DC-DC

REGULATOR

UVOUT_

OVOUT_

MAX16008/

MAX16009

Figure 2. MAX16008/MAX16009 Monitor Circuit