4

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1999 IMP, Inc.

IMP1

4/A/D

Application Information

Operation – Power Monitor

The IMP1834 supervisors simultaneously detect out-of-tolerance

power supply conditions on both 3.3V and 5V power supplies. If

reset for the failing supply voltage becomes active. When the moni-

tored supply returns to an in-tolerance state, the reset remains active

for approximately 350ms before returning to the inactive state.

On power-up, the reset signals are kept active for approximately

350ms after the power supply voltages have reached the selected

tolerance. This allows the power supply and microprocessor to

stabilize before the reset is removed.

All supply current for the IMP1834 devices is drawn from the

Reset Signal Polarity and Output Stage Structure

The IMP1834 and IMP1834A supervisors have active LOW reset

signals. The IMP1834D reset outputs are active HIGH.

The IMP1834 and IMP1834D have CMOS push-pull output

stages. The IMP1834A has open drain reset outputs.

Output Stage

IMP Part

RESET Polarity

Configuration

IMP1834

LOW

Push-Pull

IMP1834EMA

LOW

Push-Pull

IMP1834S

LOW

Push-Pull

IMP1834A

LOW

Open Drain

IMP1834AEMA

LOW

Open Drain

IMP1834AS

LOW

Open Drain

IMP1834D

HIGH

Push-Pull

IMP1834DEMA

HIGH

Push-Pull

IMP1834DS

HIGH

Push-Pull

Trip Point Tolerance Selection

The 3.3VTOL and 5VTOL inputs allow independent selection of

the reset trip points. If 5VTOL is connected to the 5V supply input,

a 10% tolerance is selected. If 5VTOL is grounded, a 5% tolerance

is selected.

If 3.3VTOL is connected to the 3.3V supply input, a 20% tolerance

is selected. If 3.3VTOL is grounded, a 10% tolerance is selected.

See Table 1.

The 3.3VTOL and 5VTOL tolerance select inputs should be tied to

Figure 1. Timing Diagram: Power Up

Figure 2. Timing Diagram: Power Down

(IMP1834D Only)

1834_10.eps

RESET

RESET

RESET

RESET

RESET Slews

1834_09.eps

(IMP1834D Only)