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19-4343; Rev 0; 10/08
3Mbps RS-232 Transceivers with Low-Voltage Interface
General Description
The MAX13234E-MAX13237E are +3V to +5.5V powered EIA/TIA-232 and V.28/V.24 communications interfaces with high data-rate capabilities (up to 3Mbps), a flexible logic voltage interface, and enhanced electrostatic discharge (ESD) protection. All receiver inputs and transmitter outputs are protected to 15kV IEC 61000-4-2 Air Gap Discharge, 8kV IEC 61000-4-2 Contact Discharge, and 15kV Human Body Model. The MAX13234E/MAX13235E have two receivers and two transmitters, while the MAX13236E/MAX13237E have a single receiver and transmitter. The transmitters have a low-dropout transmitter output stage, delivering true RS-232 performance from a +3V to +5.5V supply based on a dual charge pump. The charge pump requires only four small 0.1F capacitors for operation from a +3.3V supply. All devices achieve a 1A supply current using Maxim's AutoShutdown PlusTM feature. These devices automatically enter a low-power shutdown mode when the RS-232 cable is disconnected or the devices driving the transmitter and receiver inputs are inactive for more than 30s. The MAX13234E-MAX13237E are available in spacesaving TQFN and TSSOP packages and operate over the -40C to +85C extended temperature range. Data Rate Up to 3Mbps Low-Voltage Logic Interface +3V to +5.5V Supply Voltage AutoShutdown Plus 1A Shutdown Current
Features
MAX13234E-MAX13237E
Functional Diagrams
1.62V to VCC 3.0V to 5.5V
CBYPASS1
CBYPASS2
VL C1+ C1 C1C2+ C2 C2T1IN TTL/CMOS INPUTS T2IN
VCC V+ C3
MAX13234E MAX13235E
VC4
T1OUT RS-232 OUTPUTS T2OUT
R1OUT
LOGIC-LEVEL TRANSLATION
R1IN 5k RS-232 INPUTS
Applications
Telematics GPS Systems Industrial Systems Portable Devices Wireless Modules POS Systems Communication Systems Data Cables
TTL/CMOS OUTPUTS R2OUT FORCEOFF FORCEON READY
R2IN 5k
GND
AutoShutdown Plus is a registered trademark of Maxim Integrated Products, Inc.
Functional Diagrams continued at end of data sheet.
Ordering Information/Selector Guide
PART MAX13234EEUP+ MAX13234EETP+ MAX13235EEUP+ MAX13235EETP+ MAX13236EETE+ MAX13237EETE+ DRIVERS/ RECEIVERS 2x2 2x2 2x2 2x2 1x1 1x1 MAXIMUM DATA RATE 250kbps 250kbps 3Mbps 3Mbps 250kbps 3Mbps TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 20 TSSOP 20 TQFN-EP* 20 TSSOP 20 TQFN-EP* 16 TQFN-EP* 16 TQFN-EP*
+Denotes a lead-free/RoHS-compliant package. *EP = Exposed pad.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.) VCC ...................................................................... -0.3V to +6.0V VL ......................................................................... -0.3V to +6.0V V+ ........................................................................ -0.3V to +7.0V V- ......................................................................... +0.3V to -7.0V (V+) + |(V-)| ..................................................................... +13.0V T_IN, FORCEOFF, FORCEON ..................... -0.3V to (VL + 0.3V) R_IN ................................................................................... 25V T_OUT.............................................................................. 13.2V R_OUT, READY ........................................... -0.3V to (VL + 0.3V) Short-Circuit Duration T_OUT to GND ......................................................... Continuous Continuous Power Dissipation (TA = +70C) 16-Pin TQFN (derate 20.8mW/C above +70C) ..... 1666mW 20-Pn TSSOP (derate 10.9mW/C above +70C) ...... 879mW 20-Pin TQFN (derate 21.3mW/C above +70C) ..... 1702mW Junction-to-Case Thermal Resistance (JC) (Note 1) 16-Pin TQFN ................................................................. 2C/W 20-Pin TSSOP ............................................................. 20C/W 20-Pin TQFN ................................................................. 2C/W Junction-to-Ambient Thermal Resistance (JA) (Note 1) 16-Pin TQFN ............................................................... 30C/W 20-Pin TSSOP ............................................................. 73C/W 20-Pin TQFN ............................................................... 29C/W Operating Temperature Range MAX1323x Operating Temperature Range .... -40C to +85C MAX1323x Operating Temperature Range .. -40C to +105C Storage Temperature Range ........................... -65C to +160C Lead Temperature (soldering, 10s) .................................+300C
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +3V to +5.5V, VL = +1.62V to VCC, TA = -40C to +85C, C1-C4 = 0.1F, VCC = VL, tested at 3.3V 10%. Typical values are at TA = +25C.) (Note 2)
PARAMETER Supply Voltage Logic Supply Voltage SYMBOL VCC VL FORCEOFF = FORCEON = VL, no loads VL = 0V VCC Supply Current ICC AutoShutDown Plus, FORCEOFF = VL, FORCEON = GND, all R_IN idle, all T_IN idle. FORCEOFF = GND VCC = +5.5V FORCEOFF = GND Tested at room temperature only Tested at room temperature only 2/3 x VL 60 0.01 VOL VOH IOUT = 0.8mA IOUT = -0.5mA VL - 0.6 VL - 0.1 1 0.4 CONDITIONS MIN 3 1.62 0.3 1 1 1 1 1 TYP MAX 5.5 VCC 1 10 10 10 10 10 1/3 x VL A UNITS V V mA
VCC Shutdown Current VL Supply Current VL Shutdown Current Input Threshold Low Input Threshold High Input Hysteresis Input Leakage Current RECEIVER OUTPUTS (READY) Output-Voltage Low Output-Voltage High
ICCSH IL ILSH VIL VIH
A A A V V mV A V V
LOGIC INPUTS (T_IN, FORCEON, FORCEOFF, Referred to VL)
2
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3Mbps RS-232 Transceivers with Low-Voltage Interface
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3V to +5.5V, VL = +1.62V to VCC, TA = -40C to +85C, C1-C4 = 0.1F, VCC = VL, tested at 3.3V 10%. Typical values are at TA = +25C.) (Note 2)
PARAMETER RECEIVER INPUTS Input-Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance TRANSMITTER OUTPUTS Output-Voltage Swing Output Resistance Output Short-Circuit Current Output Leakage Current VCC = 0V or +3V to +5.5V, VOUT = 12V, transmitters disabled Positive threshold, Figure 1 Negative threshold, Figure 1 Figure 1 tWU VL = 5V, Figure 1 (Note 3) 15 -2.7 -0.3 100 30 60 +0.3 All transmitter outputs loaded with 3k to GND VCC = V+ = V- = 0V, transmitter outputs = 2V 5 300 -60 -25 5.4 10M +60 +25 V
MAX13234E-MAX13237E
SYMBOL
CONDITIONS
MIN -25
TYP
MAX +25
UNITS V V
VIL VIH
TA = +25C TA = +25C
VCC = +3.3V VCC = +5V VCC = +3.3V VCC = +5V
0.6 0.8
1.2 1.5 1.5 1.8 0.5 2.4 2.4 7
V V k
3
5
mA A
AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL) Receiver Input Threshold Valid Level Receiver Input Threshold Invalid Level Receiver or Transmitter Edge-toTransmitters Enabled Receiver or Transmitter Edge-toTransmitters Shutdown 2.7 V V V s s
tAUTOSHDN VL = 5V, Figure 1 (Note 3)
TIMING CHARACTERISTICS (MAX13234E/MAX13236E) Maximum Data Rate Receiver Propagation Delay Transmitter Skew Receiver Skew tRPHL, tRPLH |tTPHL tTPLH| |tRPHL tRPLH| RL = 3k, CL = 1000pF, one transmitter switching CL = 150pF, Figures 2, 3 Figures 4, 5 (Note 4) Figures 2, 3 250 0.15 100 50 kbps s ns ns
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3V to +5.5V, VL = +1.62V to VCC, TA = -40C to +85C, C1-C4 = 0.1F, VCC = VL, tested at 3.3V 10%. Typical values are at TA = +25C.) (Note 2)
PARAMETER SYMBOL CONDITIONS VCC = +3.3V, TA = +25C, RL = 3k to 7k, measured from +3V to -3V or -3V to +3V, one transmitter switching, CL = 150pF to 1000pF RL = 3k, CL = 250pF, one transmitter switching Maximum Data Rate RL = 3k, CL = 150pF, one transmitter switching tRPHL, tRPLH |tTPHL - tTPLH| |tRPHL - tRPLH| CL = 150pF, Figures 2, 3 Figures 4, 5 (Note 4) Figures 2, 3 VCC = +3.3V, TA = +25C, RL = 3k to 7k, measured from T_OUT = +3V to -3V or -3V to +3V, one transmitter switching, CL = 150pF to 1000pF Human Body Model R_IN, T_OUT to GND IEC 61000-4-2 Air Discharge IEC 61000-4-2 Contact Discharge MIN TYP MAX UNITS
Transition-Region Slew Rate
6
30
V/s
TIMING CHARACTERISTICS (MAX13235E/MAX13237E) 1 Mbps 3 0.15 25 50 s ns ns
Receiver Propagation Delay Transmitter Skew Receiver Skew
Transition-Region Slew Rate
24
150
V/s
ESD PROTECTION 15 15 8 kV
Note 2: All devices are 100% production tested at TA = +85C. All temperature limits are guaranteed by design. Note 3: A transmitter/receiver edge is defined as a transition through the transmitter/receiver input-logic thresholds. Note 4: Transmitter skew is measured at the transmitter zero cross points.
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3Mbps RS-232 Transceivers with Low-Voltage Interface
Test Circuits/Timing Diagram
MAX13234E-MAX13237E
RECEIVER INPUTS
TRANSMITTER INPUTS
TRANSMITTER OUTPUTS tAUTOSHDN VCC READY 0 V+ V+ VCC 0 VVtWU tAUTOSHDN tWU
Figure 1. AutoShutdown Plus, and READY Timing Diagram
T_IN
T_OUT R_IN
R_OUT CL
Figure 2. Receiver Test Circuit
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
Test Circuits/Timing Diagram (continued)
R_IN
1.3V tRPHL
tR, tF 10ns
1.7V tRPLH
VOH R_OUT VOL
VL/2
VL/2
Figure 3. Receiver Propagation Delay
T_IN
T_OUT VO CL RL
Figure 4. Transmitter Test Circuit
VL T_IN 0 VO 3V T_OUT -VO tF SRF = 6/tF 0 -3V VL/2 tTPHL
tR, tF 10ns
VL/2 tTPLH 3V 0 -3V SRR = 6/tR tR
Figure 5. Transmitter Propagation Delay
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3Mbps RS-232 Transceivers with Low-Voltage Interface
Typical Operating Characteristics
(VCC = VL = 3.3V, TA = +25C, unless otherwise noted.)
MAX13234E-MAX13237E
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX13234E toc01
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX13234E toc02
SLEW RATE vs. LOAD CAPACITANCE
11 10 SLEW RATE (V/s) 9 8 7 6 SRSR+ MAX13234E/MAX13236E RL = 3k
MAX13234E toc03
6 4 OUTPUT VOLTAGE (V) 2 0 -2 -4 -6 0 500 1000 1500 2000 MAX13234E/MAX13236E RL = 3k T1 AT 250kbps V+
6 4 OUTPUT VOLTAGE (V) 2 0 -2 -4 -6 MAX13235E/MAX13237E RL = 3k T1 AT 3Mbps V+
12
V2500
V50 100 150 200 250 300
5 4 0 500 1000 1500 2000 2500
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
SLEW RATE vs. LOAD CAPACITANCE
MAX13234E toc04
VCC SUPPLY CURRENT vs. LOAD CAPACITANCE
MAX13234E toc05
VCC SUPPLY CURRENT vs. LOAD CAPACITANCE
RL = 3k T1 AT 3Mbps T2 AT 187.5kbps MAX13235E
MAX13234E toc06
75 70 SLEW RATE (V/s) 65 SR60 55 50 45 40 50 100 150 200 250 SR+ MAX13235E/MAX13237E RL = 3k
30 25 SUPPLY CURRENT (mA) 20 15 10 5 0 RL = 3k T1 AT 250kbps T2 AT 15.6kbps MAX13234E
40 35 SUPPLY CURRENT (mA) 30 25 20 15 10 5
300
0
500
1000
1500
2000
2500
50
100
150
200
250
300
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
TRANSMITTER SKEW vs. LOAD CAPACITANCE
MAX13234E toc07
TRANSMITTER SKEW vs. LOAD CAPACITANCE
MAX13234E toc08
READY TURN-ON TIME vs. TEMPERATURE
MAX13234E toc09
150 130 TRANSMITTER SKEW (ns) 110 90 70 50 30 10 -10 0 500 1000 1500 2000 MAX13234E/MAX13236E RL = 3k 1 TRANSMITTER OPERATING AT 250kbps
9 8 TRANSMITTER SKEW (ns) 7 6 5 4 3 2 1 0 MAX13235E/MAX13237E RL = 3k 1 TRANSMITTER OPERATING AT 3Mbps
100 90 READY TURN-ON TIME (s) 80 70 60 50 40
2500
50
100
150
200
250
-40
-15
10
35
60
85
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
TEMPERATURE (C)
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
Typical Operating Characteristics (continued)
(VCC = VL = 3.3V, TA = +25C, unless otherwise noted.)
READY TURN-OFF TIME vs. TEMPERATURE
MAX13234E toc10
SUPPLY CURRENT vs. DATA RATE
MAX13234E toc11
LOGIC-INPUT THRESHOLD vs. VL
2.3 LOGIC-INPUT THRESHOLD (V) 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 0.5 VIL VCC = 5.5V VIH
MAX13234E toc12
2.0 1.8 READY TURN-OFF TIME (s) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -15 10 35 60
35 30 SUPPLY CURRENT (mA) 25 20 15 10 5 0 0.001 MAX13235E 1 TRANSMITTER OPERATING RL = 3k, CL = 150pF
2.5
85
0.01
0.1 DATA RATE (kbps)
1
10
1.5
2.5
3.5 VL (V)
4.5
5.5
TEMPERATURE (C)
TRANSMITTER OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
MAX13234E toc13
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CURRENT
6 OUTPUT VOLTAGE (V) 4 2 0 -2 -4 -6 -8 V1 TRANSMITTER OPERATING, DC V+
MAX13234E toc14
8 6 OUTPUT VOLTAGE (V) 4 2 0 -2 -4 -6 -8 3.0 3.5 4.0 4.5 5.0 V+ MAX13235E/MAX13237E RL = 3k, CL = 150pF 1 TRANSMITTER OPERATING AT 1Mbps
8
V-
5.5
0
2
4 LOAD CURRENT (mA)
6
8
SUPPLY COLTAGE (V)
8
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3Mbps RS-232 Transceivers with Low-Voltage Interface
Pin Descriptions
PIN MAX13234E/ MAX13235E TSSOP 1 TQFN-EP 19 MAX13236E/ MAX13237E TQFN-EP 14 READY Ready to Transmit Output, Active-High. READY is enabled high when V- goes below -4V and the device is ready to transmit. Positive Terminal of the Voltage Doubler Charge-Pump Capacitor +5.5V Generated by the Charge Pump Negative Terminal of the Voltage Doubler Charge-Pump Capacitor Positive Terminal of the Inverting Charge-Pump Capacitor Negative Terminal of the Inverting Charge-Pump Capacitor -5.5V Generated by the Charge Pump RS-232 Transmitter Output 2 RS-232 Receiver Input RS-232 Receiver Input 2 CMOS Receiver Output. VL referred logic. CMOS Receiver Output 2. VL referred logic. Logic-Level Supply. All CMOS inputs and outputs are related to this supply. CMOS Transmitter Input. VL referred logic. CMOS Transmitter Input 2. VL referred logic. CMOS Transmitter Input 1. VL referred logic. FORCEON Input, Active-High. VL referenced logic. Drive FORCEON high to override automatic circuitry keeping transmitters on (FORCEOFF must be high). See Table 1. CMOS Receiver Output 1. VL referred logic. RS-232 Transmitter Output RS-232 Receiver Input 1 RS-232 Transmitter Output 1 Ground +3V to +5.5V Supply Voltage FORCEOFF Input, Active-Low. VL referenced logic. Drive FORCEOFF low to shut down transmitters and on-board charge pumps. All receiver and transmitter outputs are tristated. This overrides all automatic circuitry and FORCEON (Table 1). Exposed Pad. Connect EP to GND or leave unconnected. NAME FUNCTION
MAX13234E-MAX13237E
2 3 4 5 6 7 8 -- 9 -- 10 11 -- 12 13
1 20 2 3 4 5 6 -- 7 -- 8 9 -- 10 11
16 15 1 2 3 4 -- 5 -- 6 -- 7 8 -- --
C1+ V+ C1C2+ C2VT2OUT RIN R2IN ROUT R2OUT VL TIN T2IN T1IN
14
12
9
FORCEON
15 -- 16 17 18 19
13 -- 14 15 16 17
-- 10 -- -- 11 12
R1OUT TOUT R1IN T1OUT GND VCC
20
18
13
FORCEOFF
--
--
--
EP
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
Detailed Description
VL Logic Supply Input
The MAX13234E-MAX13237E feature a separate logic supply input (VL) that sets the receiver's output level (VOH), and sets the transmitter's input thresholds (VIL, V IH ). This feature allows flexibility in interfacing to UARTs or communication controllers that have different logic levels. Connect this input to the host logic supply (1.62V VL VCC).
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic output levels. The MAX13234E-MAX13237E have inverting outputs that are active when in shutdown (FORCEOFF = GND) (Table 1).
AutoShutdown Plus Mode
Drive FORCEOFF high and FORCEON low to invoke AutoShutdown Plus mode. When these devices do not sense a valid signal transition on any receiver and transmitter input for 30s, the onboard charge pumps are shut down, reducing supply current to 1A. This occurs if the RS-232 cable is disconnected or if the devices driving the transmitter and receiver inputs are inactive for more than 30s. The MAX13234E-MAX13237E turn on again when a valid transition is applied to any RS-232 receiver or transmitter input. As a result, the system saves power without requiring any control. Figure 6 and Table 1 summarize the MAX13234E- MAX13237E operating modes. The FORCEON and FORCEOFF inputs override AutoShutdown Plus circuitry. When neither control is asserted, the IC selects between these states automatically based on the last receiver or transmitter input edge received.
Dual Charge-Pump Voltage Converter
The internal power supply consists of a regulated dual charge pump that provides output voltages of +5.5V and -5.5V (inverting charge pump), over the +3.0V to +5.5V range. The charge pump operates in discontinuous mode: if the output voltages are less than +5.5V, the charge pump is enabled; if the output voltages exceed +5.5V, the charge-pump is disabled. The charge pumps require flying capacitors (C1, C2) and reservoir capacitors (C3, C4) to generate the V+ and Vsupplies. The READY output is low when the charge pumps are disabled in shutdown mode. The READY signal asserts high when V- goes below -4V.
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The MAX13234E/MAX13236E guarantee a 250kbps data rate with worst-case loads of 3k in parallel with 1000pF. The MAX13235E/MAX13237E guarantee a 1Mbps data rate with worst-case loads of 3k in parallel with 250pF, and a 3Mbps data rate with worst-case loads of 3k in parallel with 150pF. Transmitters can be paralleled to drive multiple receivers. When FORCEOFF is driven to ground or when the AutoShutdown Plus circuitry senses that all receiver and transmitter inputs are inactive for more than 30s, the transmitters are disabled and the outputs go into a high-impedance state. When powered off or shut down, the outputs can be driven to 12V. The transmitter inputs do not have pullup resistors. Connect unused inputs to GND or VL.
Hardware-Controlled Shutdown
Drive FORCEOFF low to place the MAX13234E- MAX13237E into shutdown mode.
POWERMANAGEMENT UNIT
MASTER SHDN LINE 0.1F 1M
FORCEOFF FORCEON
MAX13234E MAX13235E MAX13236E MAX13237E
Figure 7. AutoShutdown Plus Initial Turn-On to Wake Up a Mouse or Another System
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
T_IN EDGE DETECT FORCEOFF S 30s TIMER R * POWERDOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES. FORCEOFF POWERDOWN*
FORCEON AUTOSHDN
R_IN
EDGE DETECT
FORCEON
Figure 6. AutoShutdown Plus and Shutdown Logic
Table 1. Transceiver Mode Control
FORCEOFF 0 1 1 1 FORCEON X 1 0 0 R_IN or T_IN EDGE WITHIN 30s X X Yes No T_OUT High-Impedance Active Active High-Impedance R_OUT Active Active Active Active TRANSCEIVER STATUS Shutdown (Forced Off) Normal Operation (Forced On) Normal Operation in AutoShutdown Plus Shutdown in AutoShutdown Plus
X = Don't Care.
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
15kV ESD Protection
ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver outputs and receiver inputs of the MAX13234E-MAX13237E have extra protection against static electricity. Maxim's engineers have developed state-of-the-art structures to protect these pins against ESD of 15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD event, Maxim's E versions keep working without latchup. ESD protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family are characterized for protection to the following limits: 1) 15V Using the Human Body Model 2) 15kV Using IEC 61000-4-2 Air-Gap Method 3) 8kV Using IEC 61000-4-2 Contact-Discharge Method
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1500 DISCHARGE RESISTANCE DEVICE UNDER TEST HIGHVOLTAGE DC SOURCE
RC 50M to 100M CHARGE-CURRENT LIMIT RESISTOR
RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
Cs 100pF
STORAGE CAPACITOR
Cs 150pF
STORAGE CAPACITOR
Figure 8a. Human Body ESD Test Model
Figure 9a. IEC61000-4-2 ESD Test Model
I
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
100% 90%
tDL CURRENT WAVEFORM
I PEAK
10% t r = 0.7ns to 1ns t 30ns 60ns
Figure 8b. Human Body Current Waveform
Figure 9b. IEC61000-4-2 ESD Generator Current Waveform
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3Mbps RS-232 Transceivers with Low-Voltage Interface
ESD Test Conditions
ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results. larger nominal value. The capacitor's equivalent series resistance (ESR), usually rises at low temperatures influencing the amount of ripple on V+ and V-.
MAX13234E-MAX13237E
Human Body Model
Figure 8a shows the Human Body Model and Figure 8b shows the current waveform it generates when discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5k resistor.
Table 2. Required Minimum Capacitance Values
VCC (V) 3.0 to 3.6 3.15 to 3.6 4.5 to 5.5 3.0 to 5.5 C1, CBYPASS2 (F) 0.22 0.1 0.047 0.22 CBYPASS1 (F) 0.22 0.1 1 1 C2, C3, C4 (F) 0.22 0.1 0.33 1
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The MAX13234E- MAX13237E helps design equipment that meets Level 4 (the highest level) of IEC 61000-4-2, without the need for additional ESD-protection components. The major difference between tests done using the Human Body Model and IEC 61000-4-2 is higher peak current in IEC 61000-4-2, because series resistance is lower in the IEC 61000-4-2 model. Hence, the ESD withstand voltage measured to IEC 61000-4-2 is generally lower than that measured using the Human Body Model. Figure 9a shows the IEC 61000-4-2 model and Figure 9b shows the current waveform for the 8kV, IEC 61000-4-2, 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.
Power-Supply Decoupling
In most circumstances, a 0.1F VCC bypass capacitor and a 1F VL bypass capacitor are adequate. In applications that are sensitive to power-supply noise, use capacitors of the same value as charge-pump capacitor C1. Connect bypass capacitors as close to the IC as possible.
Transmitter Outputs when Exiting Shutdown
Figure 10 shows two transmitter outputs when exiting shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (one transmitter input is high, the other is low). Each transmitter is loaded with 3k in parallel with 1000pF. The transmitter outputs display no ringing or undesirable transients as they come out of shutdown. Note that the transmitters are enabled only when the magnitude of V- exceeds approximately -3V.
Applications Information
Capacitor Selection
The capacitor type used for C1-C4 is not critical for proper operation; polarized or non-polarized capacitors can be used. The charge pump requires 0.1F capacitors for VCC = +3.3V operation. For other supply voltages, see Table 2 for required capacitor values. Do not use values smaller than those listed in Table 2. 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, CBYPASS1, and CBYPASS2 to maintain the proper ratios (C1 to 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 capacitors with a
5V/div 0
FORCEON = FORCEOFF T1OUT
2V/div 0
5V/div 0
VCC = 3.3V C1-C4 = 0.1F 5s/div
T2OUT READY
Figure 10. Transmitter Outputs when Exiting Shutdown or Powering Up
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3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
High Data Rates
The MAX13234E-MAX13237E maintain the RS-232 5V minimum transmitter output voltage even at high data rates. Figure 11 shows a transmitter loopback test circuit. Figure 12 shows a loopback test result at 120kbps, and Figure 13 shows the same test at 3Mbps. In Figure 12, all transmitters were driven simultaneously at 120kbps into RS-232 loads in parallel with 1000pF. In Figure 13, a single transmitter was driven at 3Mbps, and all transmitters were loaded with an RS-232 receiver in parallel with 150pF.
1.62V to VCC
VCC
T1IN 3V/div
CBYPASS1
CBYPASS2
VL C1+ C1 C1C2+ C2 C2T_IN
VCC V+ C3*
5V/div T1OUT
R1OUT
5V/div VCC = 3.3V
MAX13236E MAX13237E
VC4
2s/div
T_OUT
Figure 12. Loopback Test Results at 120kbps
R_OUT FORCEON VCC FORCEOFF
R_IN 5k
1000pF
T1IN 3.3V/div
T1OUT
GND
5V/div
*C3 CAN BE RETURNED TO VCC OR GND.
R1OUT VCC = 3.3V
3.3V/div
Figure 11. Loopback Test Circuit
100ns/div
Figure 13. Loopback Test Results at 3Mbps
Chip Information
PROCESS: BiCMOS
14
______________________________________________________________________________________
3Mbps RS-232 Transceivers with Low-Voltage Interface
Pin Configurations
TOP VIEW TOP VIEW FORCEON R1OUT T1OUT TOP VIEW FORCEON
MAX13234E-MAX13237E
R1IN
C1+ V+ C1C2+ C2VT2OUT R2IN R2OUT
2 3 4 5 6 7 8 9 10 MAX13234E MAX13235E
19 18 17 16 15 14 13 12 11
VCC GND GND T1OUT R1IN R1OUT READY FORCEON V+ T1IN T2IN VL 20 19 VCC FORCEOFF 17 18 16
15
14
13
12
11 12 10 9 T2IN FORCEOFF VL R2OUT V+ 7 R2IN C1+ 6 T2OUT *EP 13 14 15 16 MAX13236E MAX13237E 8 7 6 5 TIN VL ROUT RIN READY 11 10 9
MAX13234E MAX13235E
8
GND 2 C2+
VCC
READY
1
20
FORCEOFF
TOUT 3 C2-
+
T1IN
+
1 C1+ 2 C13 C2+ 4 C2-
+
1
*EP 4 V-
5 VC1-
TSSOP
TQFN
*EXPOSED PAD. CONNECT EP TO GND.
TQFN
*EXPOSED PAD. CONNECT EP TO GND.
Functional Diagrams (continued)
1.62V to VCC 3.0V to 5.5V
CBYPASS1
CBYPASS2
VL C1+ C1 C1C2+ C2 C2-
VCC V+ C3
MAX13236E MAX13237E
VC4
LOGIC-LEVEL TRANSLATION
TTL/CMOS INPUT TTL/CMOS OUTPUT
T_IN
T_OUT
RS-232 OUTPUT
R_OUT FORCEOFF FORCEON READY
R_IN 5k
RS-232 INPUT
GND
______________________________________________________________________________________
15
3Mbps RS-232 Transceivers with Low-Voltage Interface MAX13234E-MAX13237E
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 20 TSSOP 20 TQFN-EP* 16 TQFN-EP* *EP = Exposed Pad. PACKAGE CODE U20-2 T2055-5 T1655-2 DOCUMENT NO. 21-0066 21-0140 21-0140
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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