MAX16063 Datasheet, PDF (10/13 Pages) Maxim Integrated Products – 1% Accurate, Low-Voltage, Quad Window Voltage Detector

1% Accurate, Low-Voltage,
Quad Window Voltage Detector
Use the following formulas to calculate the error:
I_IB
⎛
⎝⎜
R1
+
R1 R3 ⎞
R2 + R3 ⎠⎟
E_UV (%) =
V_TRIPLOW
x 100
E_OV
(%)
=
I_IB (R2 + (2 x R1))
V_TRIPHIGH
x
100
where E_UV and E_OV are the undervoltage and over-
voltage error (in %), respectively.
2) Calculate R3 based on R_TOTAL and the desired
upper trip point:
R3 = ^{VTH x RTOTAL}
V_TRIPHIGH
3) Calculate R2 based on R_TOTAL, R3, and the
desired lower trip point:
R2 = ^{VTH x RTOTAL} − R3
V_TRIPLOW
4) Calculate R1 based on R_TOTAL, R3, and R2:
R1 = R_TOTAL − R2 − R3
Overvoltage Shutdown
The MAX16063 is ideal for overvoltage-shutdown appli-
cations. Figure 3 shows a typical circuit for this applica-
tion using a pass p-channel MOSFET. The MAX16063 is
powered directly from the system voltage supply. Select
R1 and R2 to set the trip voltage. When the supply volt-
age remains below the selected threshold, a low logic
level on UVOUT_ turns on the p-channel MOSFET. In
the case of an overvoltage 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 UVIN_ inputs must be connected to V_CC, and
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-
puts are open-drain with a (30µA) internal pullup to V_CC.
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
the external pullup voltage to V_CC (Figure 5). When
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 condition and
small enough to be able to overdrive the internal pullup
current and meet output high specifications (V_OH).
Resistor values of 50kΩ to 200kΩ can generally be used.
V_SUPPLY
R1
R2
V_CC
UVIN_
R3*
MAX16063
UVOUT_
GND
LOAD
V_SUPPLY
FUSE
R1
R2
V_CC
MAX16063
UVIN_
UVOUT_
GND
LOAD
R3
SCR
*OPTIONAL. VALUES OF 10kΩ AND ABOVE ARE RECOMMENDED.
Figure 3. Overvoltage Shutdown Circuit (with External Pass
MOSFET)
Figure 4. Overvoltage Shutdown Circuit (with SCR Fuse)
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