83386EIV Просмотр технического описания (PDF) - Intersil

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83386EIV

±15kV ESD Protected, +3V to +5.5V, 1 Microamp, 250kbps, RS-232 Transmitters/Receivers with Separate Logic Supply

Intersil 

ISL83386E

When using minimum required capacitor values, make sure

that capacitor values do not degrade excessively with

temperature. If in doubt, use capacitors with a larger nominal

value. The capacitor’s equivalent series resistance (ESR)

usually rises at low temperatures and it influences the

amount of ripple on V+ and V-.

Power Supply Decoupling

In most circumstances a 0.1µF bypass capacitor is

adequate. In applications that are particularly sensitive to

power supply noise, decouple VCC to ground with a

capacitor of the same value as the charge-pump capacitor C1.

Connect the bypass capacitor as close as possible to the IC.

Transmitter Outputs when Exiting

Powerdown

Figure 3 shows the response of two transmitter outputs

when exiting powerdown mode. As they activate, the two

transmitter outputs properly go to opposite RS-232 levels,

with no glitching, ringing, nor undesirable transients. Each

transmitter is loaded with 3kΩ in parallel with 2500pF. Note

that the transmitters enable only when the magnitude of the

supplies exceed approximately 3V.

VCC

0.1µF

+

+

C1

+

C2

VCC

C1+ VCC VL V+

C1-

ISL83386E

C2+

V-

C2-

TIN

TOUT

ROUT

RIN

5k

SHDN

+

C3

+C4

1000pF

FIGURE 4. TRANSMITTER LOOPBACK TEST CIRCUIT

5V/DIV.

T1IN

5V/DIV

SHDN

T1

T1OUT

2V/DIV

T2

VCC = +3.3V

C1 - C4 = 0.1µF

TIME (20µs/DIV.)

FIGURE 3. TRANSMITTER OUTPUTS WHEN EXITING

POWERDOWN

High Data Rates

The ISL83386E maintains the RS-232 ±5V minimum

transmitter output voltages even at high data rates. Figure 4

details a transmitter loopback test circuit, and Figure 5

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 6 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.

R1OUT

VCC = +3.3V

C1 - C4 = 0.1µF

5µs/DIV.

FIGURE 5. LOOPBACK TEST AT 120kbps

5V/DIV.

T1IN

T1OUT

R1OUT

VCC = +3.3V

C1 - C4 = 0.1µF

2µs/DIV.

FIGURE 6. LOOPBACK TEST AT 250kbps

7

FN6034.1

November 19, 2004

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