ISL83387 Просмотр технического описания (PDF) - Renesas Electronics

Номер в каталоге

Компоненты Описание

производитель

ISL83387

+/-15kV ESD Protected, +3V to +5.5V, 1Microamp, 250kbps, RS-232 Transceivers with Enhanced Automatic Powerdown and a Separate Logic Supply

Renesas Electronics 

ISL83387E

5V/DIV

FORCEOFF

T1

2V/DIV

T2

VCC = +3.3V

C1 - C4 = 0.1F

TIME (20s/DIV.)

FIGURE 8. TRANSMITTER OUTPUTS WHEN EXITING

POWERDOWN

High Data Rates

The ISL83387E maintains the RS-232 5V minimum

transmitter output voltages even at high data rates. Figure 9

details a transmitter loopback test circuit, and Figure 10

illustrates the loopback test result at 120kbps. For this test,

all transmitters were simultaneously driving RS-232 loads in

parallel with 1000pF, at 120kbps. Figure 11 shows the

loopback results for a single transmitter driving 1000pF and

an RS-232 load at 250kbps. The static transmitters were

also loaded with an RS-232 receiver.

VCC

0.1F

+

+

C1

+

C2

VCC

C1+

VCC

VL V+

C1-

ISL83387E

C2+

V-

C2-

TIN

TOUT

ROUT

RIN

FORCEON

5K

FORCEOFF

+

C3

+C4

1000pF

FIGURE 9. TRANSMITTER LOOPBACK TEST CIRCUIT

FN6040 Rev 1.00

July 8, 2005

5V/DIV.

T1IN

T1OUT

R1OUT

VCC = +3.3V

C1 - C4 = 0.1F

5s/DIV.

FIGURE 10. LOOPBACK TEST AT 120kbps

5V/DIV.

T1IN

T1OUT

R1OUT

VCC = +3.3V

C1 - C4 = 0.1F

2s/DIV.

FIGURE 11. LOOPBACK TEST AT 250kbps

Interconnection with 3V and 5V Logic

Standard 3.3V powered RS-232 devices interface well with

3V and 5V powered TTL compatible logic families (e.g., ACT

and HCT), but the logic outputs (e.g., ROUTS) fail to reach

the VIH level of 5V powered CMOS families like HC, AC, and

CD4000. The ISL83387E VL supply pin solves this problem.

By connecting VL to the same supply (1.8V to 5V) powering

the logic device, the ISL83387E logic outputs will swing from

GND to the logic VCC.

15kV ESD Protection

All pins on the 3V interface devices include ESD protection

structures, but the ISL83387E incorporates advanced

structures which allow the RS-232 pins (transmitter outputs

and receiver inputs) to survive ESD events up to 15kV. The

RS-232 pins are particularly vulnerable to ESD damage

because they typically connect to an exposed port on the

exterior of the finished product. Simply touching the port

pins, or connecting a cable, can cause an ESD event that

might destroy unprotected ICs. These new ESD structures

protect the device whether or not it is powered up, protect

Page 10 of 13

Share Link: