MAX3222ECTP View Datasheet(PDF) - Maxim Integrated

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MAX3222ECTP

±15kV ESD-Protected, Down to 10nA, 3.0V to 5.5V,Up to 1Mbps, True RS-232 Transceivers

Maxim Integrated 

±15kV ESD-Protected, Down to 10nA, 3.0V to 5.5V,

Up to 1Mbps, True RS-232 Transceivers

VCC

VCC PROTECTION

DIODE

Rx

UART

GND

Tx

SHDN = GND

PREVIOUS

RS-232

5kΩ

a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM

A ACTIVE RECEIVER OUTPUT IN SHUTDOWN.

VCC

TO LOGIC

µP TRANSITION

DETECTOR

MAX3237E/MAX3241E

VCC PROTECTION

DIODE

Rx

UART

Tx

GND

R1OUTB

R1OUT

THREE-STATED

EN = VCC

T1IN

SHDN = GND

R1IN

5kΩ

T1OUT

b) NEW MAX3237E/MAX3241E: EN SHUTS DOWN RECEIVER OUTPUTS

B (EXCEPT FOR B OUTPUTS), SO NO CURRENT FLOWS TO UART IN SHUTDOWN.

B B OUTPUTS INDICATE RECEIVER ACTIVITY DURING SHUTDOWN WITH EN HIGH.

Figure 2. Detection of RS-232 Activity when the UART and

Interface are Shut Down; Comparison of MAX3237E/MAX3241E

(b) with Previous Transceivers (a)

The complementary outputs on the MAX3237E/

MAX3241E (R_OUTB) are always active, regardless of the

state of EN or SHDN. This allows the device to be used

for ring indicator applications without forward biasing

other devices connected to the receiver outputs. This is

ideal for systems where VCC drops to zero in shutdown

to accommodate peripherals such as UARTs (Figure 2).

5V/div

0

2V/div

0

SHDN

T2OUT

VCC = 3.3V

C1–C4 = 0.1µF

40µs/div

T1OUT

Figure 3. Transmitter Outputs Recovering from Shutdown or

Powering Up

MAX3222E/MAX3237E/MAX3241E/

MAX3246E Shutdown Mode

Supply current falls to less than 1µA in shutdown mode

(SHDN = low). The MAX3237E’s supply current falls

to10nA (typ) when all receiver inputs are in the invalid

range (-0.3V < R_IN < +0.3). When shut down, the

device’s charge pumps are shut off, V+ is pulled down

to VCC, V- is pulled to ground, and the transmitter out-

puts are disabled (high impedance). The time required

to recover from shutdown is typically 100µs, as shown

in Figure 3. Connect SHDN to VCC if shutdown mode is

not used. SHDN has no effect on R_OUT or R_OUTB

(MAX3237E/MAX3241E).

±15kV ESD Protection

As with all Maxim devices, ESD-protection structures

are incorporated to protect against electrostatic dis-

charges encountered during handling and assembly.

The driver outputs and receiver inputs of the

MAX3222E/MAX3232E/MAX3237E/MAX3241E/MAX3246E

have extra protection against static electricity. Maxim’s

engineers have developed state-of-the-art structures to

protect these pins against ESD of ±15kV without damage.

The ESD structures withstand high ESD in all states:

normal operation, shutdown, and powered down. After

an ESD event, Maxim’s E versions keep working without

latchup, whereas competing RS-232 products can latch

and must be powered down to remove latchup.

Furthermore, the MAX3237E logic I/O pins also have

±15kV ESD protection. Protecting the logic I/O pins to

±15kV makes the MAX3237E ideal for data cable

applications.

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