MIC2774 datasheet(8/18 Pages) MICROCHIP

8 / 18 page

MIC2774

DS20006527A-page 8



2022 Microchip Technology Inc.

4.3

Input Bias Current Effects

Now that the resistor values are known, it is possible to

calculate the maximum potential error due to input bias

current, IIN. As shown in the Electrical Characteristics

table, the maximum value of IIN is 10 nA. Note that the

typical value is a much smaller 5 pA. The magnitude of

the offset caused by IIN is given by:

EQUATION 4-4:

The typical error is about three orders of magnitude

lower than this—close to one microvolt. Generally, the

error due to input bias can be discounted. If it is to be

taken into account, simply adjust the target threshold

voltage downward by this amount and recalculate R1

and R2. The resulting value will be very close to

optimum. If accuracy is more important than the

quiescent current in the resistors, simply reduce the

value of RTOTAL to minimize offset errors.

FIGURE 4-1:

MIC2774 Example Design.

4.4

Interfacing to Processors with

Bidirectional Reset Pins

Some microprocessors have reset signal pins that are

bidirectional, rather than input-only. The Motorola

68HC11 family is one example. Because the

MIC2774N’s output is open-drain, it can be connected

directly to the processor’s reset pin using only the

pull-up resistor normally required. See Figure 4-2.

FIGURE 4-2:

Interfacing to Bidirectional

Reset Pin.

4.5

Transient Response

The MIC2774 is inherently immune to very short

negative-going glitches. Very brief transients may

exceed the voltage thresholds without tripping the

output.

In general, as shown in Figure 4-3 and Figure 4-4, the

narrower the transient, the deeper the threshold

overdrive that the MIC2774 will ignore. The graphs

represent the typical allowable transient duration for a

given amount of threshold overdrive that will not

generate a reset.

FIGURE 4-3:

Typical Input Transient

Response.

FIGURE 4-4:

Typical VDD Transient

Response.

VERROR = IIN(max) × (R1||R2)

VERROR = ±1×10-8A × 2.189×105Ω

VERROR = ±2.189×10-3V

VERROR = ±2.189 mV

/RST

VDD

/MR

GND

MIC2774L-23

/RESET

VCORE

GND

CORE

1.0V 5%

MANUAL

RESET

MICROPROCESSOR

VI/O

I/O

2.5V 5%

/RST

VDD

/MR

GND

MIC2774N-XX

/RESET

VCC

GND

MICROPROCESSOR

100

200

300

RESET COMP. OVERDRIVE, V

REF - VIN (mV)

100

500

1000

1500

2000

RESET COMP. OVERDRIVE, V

REF - VDD (mV)

MIC2774 датащи(PDF) 8 Page - Microchip Technology

MIC2774 датащи(HTML) 8 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

датащи скачать

ссылки URL