Pullup Resistor Values

(MAX6897/MAX6898)

The exact value of the pullup resistors for the open-

drain outputs is not critical, but some consideration

should be made to ensure the proper logic levels when

2.25V and the pullup voltage is 28V, you would try to

keep the sink current less than 0.5mA as shown in the

Electrical Characteristics table. As a result, the pullup

resistor should be greater than 56kΩ. For a 12V pullup,

the resistor should be larger than 24kΩ. It should be

noted that the ability to sink current is dependent on the

Typical Application Circuits

Figures 8, 9, 10 show typical applications for the

MAX6895–MAX6899. Figure 8 shows the MAX6895

used with a p-channel MOSFET in an overvoltage pro-

tection circuit. Figure 9 shows the MAX6895 in a low-

voltage sequencing application using an n-channel

MOSFET. Figure 10 shows the MAX6895 used in a mul-

tiple-output sequencing application.

Using an n-Channel Device for Sequencing

In higher power applications, using an n-channel device

reduces the loss across the MOSFETs as it offers a

lower drain-to-source on-resistance. However, an n-

Figure 9 shows the MAX6895 in a switch sequencing

application using an n-channel MOSFET.

Similarly, if a higher voltage is present in the system, the

open-drain version can be used in the same manner.

Figure 8. Overvoltage Protection

MAX6897

ENABLE

GND

P

3.3V ALWAYS ON

OUT

R1

0 TO 28V

R2

IN

CDELAY

MAX6895

ENABLE

GND

5V BUS

OUT

R1

R2

IN

CDELAY

1.2V INPUT

1.2V OUTPUT

N

MONITORED

3.3V

Figure 9. Low-Voltage Sequencing Using an n-Channel MOSFET

Ultra-Small, Adjustable

Sequencing/Supervisory Circuits

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