MAX3225CAP データシートの表示（PDF） - Maxim Integrated

部品番号

コンポーネント説明

メーカー

MAX3225CAP

1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus

Maxim Integrated 

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

+0.3V

R_IN

30µs

TIMER

INVALID

-0.3V

R

INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR

AT LEAST 30μs.

Figure 3a. INVALID Functional Diagram, INVALID Low

T_IN

EDGE

DETECT

R_IN

EDGE

DETECT

FORCEOFF

S

30sec

TIMER

R

AUTOSHDN

FORCEON

Figure 3c. AutoShutdown Plus Logic

+2.7V

R_IN

30µs

TIMER

INVALID

-2.7V

R

INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V

FOR LESS THAN 30μs.

Figure 3b. INVALID Functional Diagram, INVALID High

FORCEOFF

FORCEON

AUTOSHDN

* POWERDOWN IS ONLY AN INTERNAL SIGNAL.

IT CONTROLS THE OPERATIONAL STATUS OF

THE TRANSMITTERS AND THE POWER SUPPLIES.

Figure 3d. Power-Down Logic

POWERDOWN*

Table 2. INVALID Truth Table

RS-232 SIGNAL

PRESENT AT ANY

RECEIVER INPUT

Yes

No

INVALID OUTPUT

High

Low

peripheral transmitters are turned off, and the UART dri-

ving the transmitter inputs is inactive. The system turns

on again when a valid transition is applied to any

RS-232 receiver or transmitter input. As a result, the sys-

tem saves power without changes to the existing BIOS

or operating system.

Figures 3a and 3b depict valid and invalid RS-232

receiver voltage levels. INVALID indicates the receiver

input’s condition, and is independent of FORCEON and

FORCEOFF states. Figure 3 and Tables 1 and 2 sum-

marize the operating modes of the MAX3224–

MAX3227/MAX3244/MAX3245 devices. FORCEON and

FORCEOFF override AutoShutdown Plus circuitry.

When neither control is asserted, the IC selects

+2.7V

+0.3V

0

-0.3V

-2.7V

INVALID HIGH

INDETERMINATE

INVALID LOW

INDETERMINATE

INVALID HIGH

Figure 4a. Receiver Positive/Negative Thresholds for INVALID

between these states automatically based on the last

receiver or transmitter input edge received.

When shut down, the device’s charge pumps turn off,

V+ is pulled to VCC, V- is pulled to ground, the transmit-

ter outputs are high impedance, and READY

(MAX3224–MAX3227) is driven low. The time required

to exit shutdown is typically 100µs (Figure 8).

10 ______________________________________________________________________________________

Share Link: