MAX3224EETP+ Maxim Integrated Products, MAX3224EETP+ Datasheet - Page 14

• Manufacturer Part Number: MAX3224EETP+
• Description: IC TXRX RS232 250KBPS SD 20-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX3224EETP+

• Number Of Drivers/receivers: 2/2
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 20-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

±15kV ESD-Protected, 1µA, 1Mbps 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
The IEC 1000-4-2 standard covers ESD testing and per-
formance of finished equipment; it does not specifically
refer to integrated circuits. The MAX3224E–MAX3227E,
MAX3244E/MAX3245E help you design equipment that
meets Level 4 (the highest level) of IEC 1000-4-2, with-
out the need for additional ESD-protection components.
The major difference between tests done using the
Human Body Model and IEC 1000-4-2 is higher peak
current in IEC 1000-4-2, because series resistance is
lower in the IEC 1000-4-2 model. Hence, the ESD with-
stand voltage measured to IEC 1000-4-2 is generally
lower than that measured using the Human Body
Model. Figure 7a shows the IEC 1000-4-2 model and
Figure 7b shows the current waveform for the 8kV, IEC
1000-4-2, Level 4, ESD Contact-Discharge Method.
The Air-Gap Method involves approaching the device
with a charged probe. The Contact-Discharge Method
connects the probe to the device before the probe is
energized.
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis-
tance. Its objective is to emulate the stress caused by
contact that occurs with handling and assembly during
manufacturing. Of course, all pins require this protec-
tion during manufacturing, not just RS-232 inputs and
outputs. Therefore, after PC board assembly, the
Machine Model is less relevant to I/O ports.
The capacitor type used for C1–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
Table 3. Required Minimum Capacitance
Values
14
__________Applications Information
3.15 to 3.6
3.0 to 3.6
4.5 to 5.5
3.0 to 5.5
______________________________________________________________________________________
V
(V)
CC
C1, C
0.047
(
0.22
0.22
0.1
µ
BYPASS
F)
Capacitor Selection
Machine Model
C2, C3, C4
IEC 1000-4-2
(
0.22
0.33
µ
0.1
1
F)
can be used. The charge pump requires 0.1µF capaci-
tors for 3.3V operation. For other supply voltages, see
Table 3 for required capacitor values. Do not use val-
ues smaller than those listed in Table 3. Increasing the
capacitor values (e.g., by a factor of 2) reduces ripple
on the transmitter outputs and slightly reduces power
consumption. C2, C3, and C4 can be increased without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4,
and C
the other capacitors).
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci-
tors with a larger nominal value. The capacitor’s equiv-
alent series resistance (ESR), which usually rises at low
temperatures, influences the amount of ripple on V+
and V-.
In most circumstances, a 0.1µF V
is adequate. In applications that are sensitive to power-
supply noise, use a capacitor of the same value as
charge-pump capacitor C1. Connect bypass capaci-
tors as close to the IC as possible.
Figure 8 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two trans-
mitter outputs are shown going to opposite RS-232 lev-
els (one transmitter input is high, the other is low). Each
Figure 8. Transmitter Outputs when Exiting Shutdown or
Powering Up
5V/div
2V/div
5V/div
0
0
0
BYPASS
V
C1–C4 = 0.1μF
CC
= 3.3V
, to maintain the proper ratios (C1 to
5μs/div
Power-Supply Decoupling
when Exiting Shutdown
Transmitter Outputs
CC
bypass capacitor
FORCEON = FORCEOFF
T1OUT
T2OUT
READY