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Issue A

LANSDALE Semiconductor, Inc.

ML145407

ESD CONSIDERATIONS

ESD protection on IC devices that have their pins accessible

to the outside world is essential. High static voltages applied to

the pins when someone touches them either directly or indi-

rectly can cause damage to gate oxides and transistor junctions

by coupling a portion of the energy from the I/O pin to the

power supply busses of the IC. This coupling will usually

occur through the internal ESD protection diodes. The key to

protecting the IC is to shunt as much of the energy to ground

as possible before it enters the IC. Figure 7 shows a technique

which will clamp the ESD voltage at approximately + 15 V

using the MMBZ15VDLT1. Any residual voltage which

appears on the supply pins is shunted to ground through the

0.1 µF capacitors.

OPERATION WITH SMALLER VALUE CHARGE

PUMP CAPS

The ML145407 is characterized in the electrical tables using

10 µF charge pump caps to illustrate its capability in driving a

companion ML145406 or ML145403. If there is no require-

ment to support a second interface device and/or the charge

pump is not being used to power any other components, the

ML145407 is capable of complying with EIA–232–E and V.28

with smaller value charge pump caps.Table 1 summarizes driv-

er performance with both 2.2 µF and1.0µF charge pump caps.

14

600

16

TIP

13

BYPASS

DTMF

INPUT

RDSI

20 k

Ω

CDSI RTLA

+ 5 V

20

6

9

8

3

11

5

TLA

DSI

TxA

RxA2

1

17

15

VDD

Xin

Xout

CD

TxD

RxD

SQT

LB

MODE

CDA

VSS

CDT

VAG

FB

ExI

RxA1

RTx

18

10

19

4

600:600

CFB

+

10 k

Ω

RING

VDD

VDD

BYPASS

VSS

CCDT

12

7

2

10 k

Ω

10 k

Ω

10 k

Ω

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

10

µF

1.0

µF

3.579

MHz

CCDA

3

1

15

16

13

17

19

6

5

8

7

9

8

2

3

7

2

4

VSS

GND

DI3

DI2

DO1

DI1

C2 +

C2 – VDD

VCC C1 –

C1 +

Tx1

Rx1

Tx2

Rx2

Rx3

* Line protection circuit

ML145442

OR

ML145443

ML145407

1.0

µF

1.0

µF

1.0

µF

+

EIA–232–E

DB–25

CONNECTOR

0.1

µF

0.1

µF

0.1

µF

*

Figure 4. 5 V, 300 Baud Modem with EIA–232–E Interface

Table 1. Typical Performance

Parameter

2.2

µF

1.0

µF

Tx VOH @ 25°C

7.3

7.2

Tx VOH @ 85°C

7.2

7.1

Tx VOL @ 25°C

– 6.5

– 6.4

Tx VOL @ 85°C

– 6.1

– 6.0

Tx Slew Rate @ 25

°C

8.0 V/

µs

8.0 V/

µs

Tx Slew Rate @ 85

°C

7.0 V/

µs

7.0 V/

µs