APPLICATIONS INFORMATION
ESD CONSIDERATIONS
ESD protection on IC devices that have their pins acces-
sible to the outside world is essential. High static voltages
applied to the pins when someone touches them either di-
rectly or indirectly 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 cou-
pling 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. Fig-
ure 7 shows a technique which will clamp the ESD voltage at
approximately + 15 V using the MMBZ15VDLT1. Any resid-
ual 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 MC145407 is characterized in the electrical tables
using 10
µF
charge pump caps to illustrate its capability in
driving a companion MC145406 or MC145403. If there is no
requirement to support a second interface device and/or the
charge pump is not being used to power any other com-
ponents, the MC145407 is capable of complying with
EIA–232–E and V.28 with smaller value charge pump caps.
Table 1 summarizes driver performance with both 2.2
µF
and
1.0
µF
charge pump caps.
Table 1. Typical Performance
Parameter
Tx VOH @ 25°C
Tx VOH @ 85°C
Tx VOL @ 25°C
Tx VOL @ 85°C
Tx Slew Rate @ 25°C
Tx Slew Rate @ 85°C
2.2
µF
7.3
7.2
– 6.5
– 6.1
8.0 V/µs
7.0 V/µs
1.0
µF
7.2
7.1
– 6.4
– 6.0
8.0 V/µs
7.0 V/µs
+5V
0.1
µF
20
DTMF
INPUT
RDSI
20 kΩ
CDSI RTLA
0.1
µF
RTx
10
µF
600
+
*
RING
VDD
0.1
µF
VDD BYPASS
0.1
µF
VSS BYPASS
CFB
10
0.1
µF
19
600:600
18
ExI
FB
MODE
VSS
12
CDA
1
6
TLA
VDD
Xin
Xout
CD
9
8
3
3.579
MHz
1.0
µF
0.1
µF
3
1
1.0
µF
17 +
C2 – VDD
0.1
µF
19
VCC C1 –
C1 +
Tx1
Rx1
MC145407
10 kΩ
LB
2
10 kΩ
13
7
CCDA
0.1
µF
1.0
µF
VSS
4
Rx3
GND
2
DI3
Tx2
Rx2
8
7
9
3
7
6
5
2
8
EIA–232–E
DB–25
CONNECTOR
1.0
µF
DSI
17
TxA
15
RxA2
11
TxD
5
RxD
10 kΩ
SQT
14
C2 +
15 DI1
16 DO1
13
DI2
10 kΩ
TIP
16
MC145442
OR
RxA1
MC145443
VAG
4
CDT
0.1
µF
CCDT
* Line protection circuit
Figure 4. 5 V, 300 Baud Modem with EIA–232–E Interface
MC145407
6
MOTOROLA
MOTOROLA [ MOTOROLA, INC ]
