ADM3251E Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
NC
1
V
CC
2
V
CC
3
GND
4
V
ISO
20
V+
19
C1+
18
C1–
17
GND
5
T
OUT
16
GND
6
R
IN
15
GND
7
C2+
14
R
OUT
8
C2–
13
T
IN
9
V–
12
GND
10
GND
ISO
11
NC = NO CONNECT
ADM3251E
TOP VIEW
(Not to Scale)
07388-002
Figure 2. Pin Configuration
Table 8. Pin Function Descriptions
Pin No. Mnemonic Description
1 NC No Connect. This pin should always remain unconnected.
2, 3 V
CC
Power Supply Input. A 0.1 µF decoupling capacitor is required between V
CC
and ground. When a voltage
between 4.5 V and 5.5 V is applied to the V
CC
pin, the integrated dc-to-dc converter is enabled. If this voltage
is lowered to between 3.0 V and 3.7 V, the integrated dc-to-dc converter is disabled.
4, 5, 6, 7, 10 GND Ground.
8 R
OUT
Receiver Output. This pin outputs CMOS logic levels.
9 T
IN
Transmitter (Driver) Input. This pin accepts CMOS levels.
11 GND
ISO
Ground Reference for Isolated RS-232 Side.
12 V− Internally Generated Negative Supply.
13, 14 C2−, C2+ Positive and Negative Connections for Charge Pump Capacitors. External Capacitor C2 is connected between
these pins; a 0.1 µF capacitor is recommended, but larger capacitors up to 10 µF can be used.
IN
Receiver Input. This input accepts RS-232 signal levels.
16 T
OUT
Transmitter (Driver) Output. This outputs RS-232 signal levels.
17, 18 C1−, C1+ Positive and Negative Connections for Charge Pump Capacitors. External Capacitor C1 is connected between
these pins; a 0.1 µF capacitor is recommended, but larger capacitors up to 10 µF can be used.
19 V+ Internally Generated Positive Supply.
20 V
ISO
Isolated Supply Voltage for Isolator Secondary Side. A 0.1 µF decoupling capacitor is required between V
ISO
and ground. When the integrated dc-to-dc converter is enabled, the V
ISO
pin should not be used to power
external circuitry. If the integrated dc-to-dc converter is disabled, power the secondary side by applying a
voltage in the range of 3.0 V to 5.5 V to this pin.
Rev. G | Page 8 of 16
