
3
I/O Pins Configuration Table
Pin
1
Symbol
LED A
Description
LED Anode
I/O Type
Input
Function
This pin can be connected directly to V
CC
(i.e., without series resistor)
at less than 3 V. Please refer to Table 1 for V
CC
versus Series Resistor, R1.
Leave this pin unconnected.
This pin is used to transmit serial data when SD/Mode pin is low. If this
pin is held high longer than ~100
μ
s, the LED would be turned off when
used in conjunction with the SD/Mode pin. TXD is low at initialization.
This pin is capable of driving a standard CMOS or TTL load. No external
pull-up or pull-down resistor is required. It is in tri-state mode when the
transceiver is in shutdown mode and during digital serial programming
operations. RXD is high at initialization.
The transceiver is in shutdown mode if this pin is high for more than
400
μ
s. On the falling edge of this signal, the state of the TXD pin sampled
and used to set receiver low bandwidth (TXD=low) or high bandwidth
(TXD=high) mode. See Figure 3 and Figure 4 for bandwidth selection
timings. SD is low at initialization.
Regulated, 2.7 to 5.25 Volts.
2
3
LED C
TXD
LED Cathode
Transmit Data
Output
Input,
Active High
4
RXD
Receive Data
Output,
Active Low
5
SD/Mode Shutdown/
Input,
Active High
Mode Select
6
V
CC
Supply
Voltage
No Connect
Ground
EMI Shield
Supply
Voltage
No Connect
Ground
EMI Shield
7
8
–
NC
GND
Shield
Connect to system ground.
Connect to system ground via a low inductance trace. For best
performance, do not connect directly to the transceiver pin GND.
Recommended Application Circuit Components
Component
R1
Recommended Value
0
±
5%, 0.5 Watt, for 2.7 V
1.8
±
5%, 0.5 Watt, for 3.0 V
4.7
±
5%, 0.5 Watt, for 3.3 V
6.8
±
5%, 0.5 Watt, for 3.5 V
0.47
μ
F
±
20%, X7R Ceramic
6.8
μ
F
±
20%, Tantalum
Notes
CX1
CX2
1
2
Notes:
1. CX1 must be placed within 0.7 cm of the HSDL-3603 to obtain optimum noise immunity.
2. In environments with noisy power supplies, supply rejection performance can be enhanced
by including CX2, as shown in Figure 1: ”HSDL-3603 Functional Block Diagram“ on Page 2.