Low-Voltage, High-Accuracy, Quad Window

Voltage Detectors in Thin QFN

10

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Use the following formulas to calculate the error:

voltage error (in %), respectively.

upper trip point:

desired lower trip point:

Overvoltage Shutdown

The MAX16008/MAX16009 are ideal for overvoltage-

shutdown applications. Figure 3 shows a typical circuit

for this application using a pass p-channel MOSFET.

The MAX16008/MAX16009 are powered directly from

the system voltage supply. Select R1 and R2 to set the

trip voltage. When the supply voltage remains below the

selected threshold, a low logic level on UVOUT_ turns

on the p-channel MOSFET. In the case of an overvolt-

age event, UVOUT_ goes high turning off the MOSFET,

and shuts down the power to the load.

Figure 4 shows a similar application using a fuse and a

silicon-controlled rectifier (SCR). An overvoltage event

turns on the SCR and shorts the supply to ground. The

surge of current through the short circuit blows the fuse

and terminates the current to the load. Select R3 so that

the gate of the SCR is properly biased when UVOUT_

goes high.

Unused Inputs

any unused OVIN_ inputs must be connected to GND.

UVOUT_/OVOUT_ Outputs

UVOUT_ and OVOUT_ outputs assert low when UVIN_

and OVIN_, respectively, drop below or exceed their

specified thresholds. The undervoltage/overvoltage out-

For many applications, no external pullup resistor is

required to interface with other logic devices. An external

pullup resistor to any voltage up to 5.5V overdrives the

internal pullup if interfacing to different logic supply volt-

ages. Internal circuitry prevents reverse current flow from

choosing the external pullup resistor, the resistance

value should be large enough to ensure that the output

can sink the necessary current during a logic-low condi-

tion and small enough to be able to overdrive the internal

pullup current and meet output high specifications

RR

R

R

TOTAL

12

3

=−

−

R

Vx R

V

R

TH

TOTAL

TRIPLOW

23

=−

R

Vx R

V

TH

TOTAL

TRIPHIGH

3

=

E

IR

RR

RR

V

x

E

IR

x R

V

x

UV

IB

TRIPLOW

OV

IB

TRIPHIGH

(%)

(%)

((

))

=

+

+

⎛

⎝⎜

⎞

⎠⎟

=

+

1

13

23

21

100

2

100

LOAD

UVIN_

R1

R2

UVOUT_

MAX16008/

MAX16009

GND

R3*

*OPTIONAL. VALUES OF 10k

Ω AND ABOVE ARE RECOMMENDED.

Figure 3. Overvoltage Shutdown Circuit (with External Pass

MOSFET)

LOAD

SCR

UVIN_

R1

R2

R3

UVOUT_

MAX16008/

MAX16009

GND

FUSE

Figure 4. Overvoltage Shutdown Circuit (with SCR Fuse)