MAX3349EA Просмотр технического описания (PDF) - Maxim Integrated

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производитель

MAX3349EA

USB 2.0 Full-Speed Transceiver with UART Multiplexing Mode

Maxim Integrated 

USB 2.0 Full-Speed Transceiver with UART

Multiplexing Mode

Timing Diagrams (continued)

OE

VP/VM

tPLZ_SE

OE

VP/VM

D+/D- CONNECTED TO GND,

VP/VM CONNECTED

TO PULLUP

tPZL_SE

D+/D- CONNECTED TO +3V,

VP/VM CONNECTED

TO PULLDOWN

MAX3349EA D+/D-

TEST

POINT

1. ENABLE TIME (D+/D-)

MEASUREMENT

15kΩ

2. VP/VM TO D+/D-

CL

PROPAGATION DELAY

50pF 3. D+/D- RISE/FALL TIMES

Figure 7. Test Circuit for Enable Time, Transmitter Propagation

Delay, and Transmitter Rise/Fall Time

MAX3349EA RCV/VP/VM

TEST

POINT

1. D+/D- TO RCV/VM/VP

PROPAGATION DELAYS

CL

15pF

Figure 8. Test Circuit for Receiver Propagation Delay

tPHZ_SE

tPZH_SE

Figure 5. Receiver Enable and Disable Timing

MAX3349EA

TEST

POINT 220Ω

D+/D-

CL

50pF

1. DISABLE TIME (D+/D-)

MEASUREMENT

V = 0 FOR tPHZ

V = VTRM FOR tPLZ

RC

RD

1MΩ

1.5kΩ

CHARGE-CURRENT-

LIMIT RESISTOR

DISCHARGE

RESISTANCE

HIGH-

VOLTAGE

DC

SOURCE

Cs

100pF

STORAGE

CAPACITOR

DEVICE

UNDER

TEST

Figure 6. Test Circuit for Disable Time

Figure 9. Human Body ESD Test Model

Detailed Description

The MAX3349EA ±15kV ESD-protected, USB transceiver

provides a full-speed USB interface to a microprocessor or

ASIC. The device supports enumeration, suspend, and

VBUS detection. A special UART multiplexing mode routes

external UART signals (Rx and Tx) to D+ and D-, allowing

the use of a shared connector to reduce cost and part count

for mobile devices.

The UART interface allows mobile devices such as PDAs,

cellular phones, and digital cameras to use either UART or

USB signaling through the same connector. The

MAX3349EA features a separate UART voltage supply

input. The MAX3349EA supports a maximum UART

baud rate of 921kbaud.

Upon connection to a USB host, the MAX3349EA

enters USB mode and provides a full-speed USB 2.0

compliant interface through VP, VM, RCV, and OE. The

MAX3349EA features internal series resistors on D+

and D-, and an internal 1.5kΩ pullup resistor to D+ to

allow the device to logically connect and disconnect

from the USB bus while plugged in. A suspend mode is

provided for low-power operation. D+ and D- are pro-

tected from electrostatic discharge (ESD) up to ±15kV.

To ensure full ±15kV ESD protection, bypass VBUS to

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