19-0272; Rev 4; 4/12 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers ____________________________Features The MAX338/MAX339 are monolithic, CMOS analog multiplexers (muxes). The 8-channel MAX338 is designed to connect one of eight inputs to a common output by control of a 3-bit binary address. The dual, 4channel MAX339 is designed to connect one of four inputs to a common output by control of a 2-bit binary address. Both devices can be used as either a mux or a demux. On-resistance is 400 max, and the devices conduct current equally well in both directions. o On-Resistance, <400 max These muxes feature extremely low off leakages (less than 20pA at +25C), and extremely low on-channel leakages (less than 50pA at +25C). The new design offers guaranteed low charge injection (1.5pC typ) and electrostatic discharge (ESD) protection greater than 2000V, per method 3015.7. These improved muxes are pin-compatible upgrades for the industry-standard DG508A and DG509A. For similar Maxim devices with lower leakage and charge injection but higher on-resistance, see the MAX328 and MAX329. The MAX338/MAX339 operate from a single +4.5V to +30V supply or from dual supplies of 4.5V to 20V. All control inputs (whether address or enable) are TTL compatible (+0.8V to +2.4V) over the full specified temperature range and over the 4.5V to 18V supply range. These parts are fabricated with Maxim's 44V silicon-gate process. o Plug-In Upgrade for Industry-Standard DG508A/DG509A ________________________Applications Data-Acquisition Systems Sample-and-Hold Circuits Test Equipment Heads-Up Displays Military Radios Communications Systems Guidance and Control Systems PBX, PABX o Transition Time, <500ns o On-Resistance Match, <10 o NO-Off Leakage Current, <20pA at +25C o 1.5pC Charge Injection o Single-Supply Operation (+4.5V to +30V) Bipolar-Supply Operation (4.5V to 20V) o Rail-to-Rail Signal Handling o TTL/CMOS-Logic Compatible o ESD Protection >2000V, per Method 3015.7 Ordering Information TEMP RANGE PIN-PACKAGE MAX338CEE+ PART 0C to +70C 16 QSOP MAX338CPE+ 0C to +70C 16 PDIP MAX338CSE+ 0C to +70C 16 Narrow SO MAX338C/D 0C to +70C Dice* MAX338EEE+ -40C to +85C 16 QSOP MAX338ETE+ -40C to +85C 16 TQFN-EP** (5mm x 5mm) Ordering Information continued at end of data sheet. *Contact factory for dice specifications. **EP = Exposed Pad ***Contact factory for availability. +Denotes a lead(Pb)-free/RoHS-compliant package. _____________________Pin Configurations/Functional Diagrams/Truth Tables TOP VIEW V+ A0 1 16 A1 NO1 EN 2 15 A2 NO2 V- 3 14 GND NO3 NO1 4 13 V+ NO4 MAX338 NO2 5 12 NO5 NO3 6 11 NO6 NO4 7 10 NO7 COM 8 9 DIP/SO/QSOP Pin Configurations/Functional Diagrams/Truth Tables continued at end of data sheet. V- GND COM NO5 NO6 NO7 NO8 NO8 CMOS DECODE LOGIC A2 A1 A0 EN MAX338 8-CHANNEL SINGLE-ENDED MULTIPLEXER ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX338/MAX339 General Description MAX338/MAX339 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers ABSOLUTE MAXIMUM RATINGS Voltage Referenced to VV+ ............................................................................-0.3V, 44V GND .........................................................................-0.3V, 25V Digital Inputs, NO, COM (Note 1)...........(V- - 2V) to (V+ + 2V) or 30mA (whichever occurs first) Continuous Current (any terminal) ......................................30mA Peak Current, NO or COM (pulsed at 1ms, 10% duty cycle max) ..........................100mA Continuous Power Dissipation (TA = +70C) Plastic DIP (derate 10.53mW/C above +70C) ..........842mW Narrow SO (derate 8.70mW/C above +70C) ............696mW 16 QSOP (derate 8.3mW/C above +70C) ..............666.7mW 16-Pin TQFN (derate 20.8mW/C above +70C) ....1666.7mW CERDIP (derate 10.00mW/C above +70C) ...............800mW Operating Temperature Ranges MAX33_C__ ........................................................0C to +70C MAX33_E__......................................................-40C to +85C MAX33_MJE, MSE .........................................-55C to +125C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C Soldering Temperature (reflow) Lead(Pb)-free packages..............................................+260C Packages containing lead(Pb).....................................+240C Signals on NO, COM, EN, A0, A1, or A2 exceeding V+ or V- are clamped by internal diodes. Limit forward current to maximum current ratings. Note 1: 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--Dual Supplies (V+ = +15V, V- = -15V, VGND = 0V, VAH = +2.4V, VAL = +0.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL MIN CONDITIONS TYP MAX (Note 2) UNITS SWITCH Analog Signal Range On-Resistance VNO, VCOM RON On-Resistance Matching Between Channels RON NO-Off Leakage Current (Note 5) INO(OFF) COM-Off Leakage Current (Note 5) (Note 3) -15 INO = 0.2mA, VCOM = 10V TA = +25C INO = 0.2mA, VCOM = 10V (Note 4) TA = +25C VCOM = +10V, VNO = 10V, VEN = 0V TA = +25C VNO = 10V, VCOM = +10V, MAX338 VEN = 0V TA = +25C VNO = +10V, VCOM = 10V, MAX339 VEN = 0V TA = +25C ICOM(OFF) 220 TA = TMIN to TMAX TA = TMIN to TMAX TA = TMIN to TMAX TA = TMIN to TMAX TA = TMIN to TMAX M M M COM-On Leakage Current (Note 5) 2 ICOM(ON) TA = TMIN to TMAX C, E M TA = +25C TA = TMIN to TMAX C, E M nA 0.05 3.25 -40 40 0.005 -1.65 0.05 nA 1.65 -20 20 0.006 -3.25 0.05 3.25 -40 -0.05 20 0.005 -3.25 -0.05 V 0.02 1.25 -20 -0.05 C, E 0.001 -1.25 -0.05 C, E 10 5 15 -0.02 C, E 400 500 4 1.5 TA = +25C VCOM = 10V, MAX338 VNO = 10V, sequence each switch MAX339 on 15 40 0.008 0.05 -1.65 1.65 -20 20 _______________________________________________________________________________________ nA 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers (V+ = +15V, V- = -15V, VGND = 0V, VAH = +2.4V, VAL = +0.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX (Note 2) UNITS INPUT Input Current with Input Voltage High IAH VA = 2.4V or 15V -1.0 Input Current with Input Voltage Low IAL VEN = 0V or 2.4V, VA = 0V -1.0 SUPPLY Power-Supply Range 4.5 VEN = VA = 0V Positive Supply Current Negative Supply Current I+ I- VEN = 2.4V, VA(ALL) = 2.4V VEN = 0V or 2.4V, VA(ALL) = 0V, 2.4V or 5V DYNAMIC Transistion Time Break-Before-Make Interval tTRANS tOPEN Figure 2 Figure 4 Enable Turn-On Time tON(EN) Figure 3 Enable Turn-Off Time tOFF(EN) Figure 3 Charge Injection (Note 3) 0.001 Q TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = +25C TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX 50 290 -1 -10 10 200 140 160 100 CL = 100pF, VNO = 0V, RS = 0, Figure 6 TA = +25C 1.5 1.0 A 1.0 A 20 100 150 500 600 1 10 V 500 500 750 500 750 5 A A A ns ns ns ns pC Off Isolation (Note 6) VISO VEN = 0V, RL = 1k, f = 100kHz TA = +25C -75 dB Crosstalk Between Channels VCT VEN = 2.4V, f = 100kHz, VGEN = 1VP-P, RL = 1k, Figure 7 TA = +25C -92 dB Logic Input Capacitance CIN f = 1MHz TA = +25C 2 pF f = 1MHz, VEN = VNO = 0V, Figure 8 TA = +25C 3 pF NO-Off Capacitance COM-Off Capacitance COM-On Capacitance CNO(OFF) f = 1MHz, VEN = 0.8V, CCOM(OFF) VCOM = 0V, Figure 8 f = 1MHz, VEN = 2.4V, CCOM(ON) VCOM = 0V, Figure 8 MAX338 11 TA = +25C MAX339 pF 6 MAX338 16 TA = +25C MAX339 pF 9 _______________________________________________________________________________________ 3 MAX338/MAX339 ELECTRICAL CHARACTERISTICS--Dual Supplies (continued) MAX338/MAX339 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers ELECTRICAL CHARACTERISTICS--Single Supply (V+ = +12V, V- = 0V, VGND = 0V, VAH = +2.4V, VAL = +0.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX (Note 2) UNITS SWITCH Analog Signal Range On-Resistance VNO, VCOM RON (Note 3) INO = 0.2mA VCOM = 3V or 10V 0 12 V TA = +25C 460 650 TA = +25C 210 500 ns TA = +25C 280 500 ns TA = +25C 110 500 ns TA = +25C 1.8 5 pC DYNAMIC Transition Time (Note 3) tTRANS Enable Turn-On Time (Note 3) tON(EN) Enable Turn-Off Time (Note 3) tOFF(EN) Charge Injection (Note 3) Q VNO1 = 8V, VNO8 = 0V, VIN = 2.4V, Figure 1 VINH = 2.4V, VINL = 0V, VNO1 = 5V, Figure 3 VINH = 2.4V, VINL = 0V, VNO1 = 5V, Figure 3 CL = 100pF, VNO = 0V, RS = 0 Note 2: The algebraic convention where the most negative value is a minimum and the most positive value a maximum is used in this data sheet. Note 3: Guaranteed by design. Note 4: RON = RON(MAX) - RON(MIN). Note 5: Leakage parameters are 100% tested at the maximum rated hot temperature and guaranteed by correlation at +25C. Note 6: Worst-case isolation is on channel 4 because of its proximity to the drain pin. Off isolation = 20log VCOM/VNO, where VCOM = output and VNO = input to off switch. 4 _______________________________________________________________________________________ 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers ON-RESISTANCE vs. VCOM (DUAL SUPPLIES) V+ = +15V V- = -15V +125C 1200 300 15V 200 RON () 10V 300 +25C 200 20V 600 +15V 400 100 +20V 200 0 0 -10 -5 0 5 10 15 20 -15 -10 -5 VCOM (V) +25C -55C 200 V+ = +15V V- = -15V 1 ICOM (OFF) 0.1 0 15 1 0.1 ICOM(ON) INO (OFF) 0.001 0.0001 -55 -35 -15 5 25 45 65 -55 -35 -15 85 105 125 25 45 5 85 105 125 65 TEMPERATURE (C) TEMPERATURE (C) CHARGE INJECTION vs. VCOM SUPPLY CURRENT vs. TEMPERATURE TRANSITION TIME vs. POWER SUPPLIES 15V I+, I- (A) +12V 0 1 0.01 -30 0.001 SINGLE SUPPLY 600 500 400 300 I-20 MAX338/9 TOC-09 800 700 0.1 -10 RL = 1k 900 10 +5V 10 I+, VA = 0V tTRANS (nS) 20 I+, VA(ALL) = 2.4V 100 1000 MAX338/9 TOC-08 1000 MAX338/9 TOC-07 CL = 100pF V- = 0V 20 10 VCOM (V) 40 30 V+ = +15V V- = -15V 100 0.01 0.0001 10 15 ON LEAKAGE vs. TEMPERATURE 10 0.001 5 10 1000 0.01 100 0 5 VCOM (V) MAX338/9 TOC-05 100 OFF LEAKAGE (nA) +125C +85C 300 0 15 1000 MAX338/9 TOC-04 V+ = +15V V- = 0V 400 10 OFF LEAKAGE vs. TEMPERATURE 700 500 5 VCOM (V) ON-RESISTANCE vs. VCOM OVER TEMPERATURE (SINGLE SUPPLY) 600 0 MAX338/9 TOC-06 -15 ON LEAKAGE (nA) 0 -20 RON () 800 +12V -55C 100 Qj (pC) +5V 1000 +85C RON () RON () 400 MAX338/9 TOC-03 5V 1400 MAX338/9 TOC-02 400 MAX338/9 TOC-01 600 500 ON-RESISTANCE vs. VCOM (SINGLE SUPPLY) ON-RESISTANCE vs. VCOM OVER TEMPERATURE (DUAL SUPPLIES) DUAL SUPPLIES 200 100 -15 -10 -5 0 VCOM (V) 5 10 15 0 -55 -35 -15 5 25 45 65 TEMPERATURE (C) 85 105 125 0 5 OR 5V 10 OR 10V (SINGLE) (SINGLE) 15 20 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5 MAX338/MAX339 __________________________________________Typical Operating Characteristics (TA = +25C, unless otherwise noted.) MAX338/MAX339 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers ______________________________________________________________Pin Description PIN MAX338 NAME MAX339 DIP/SO/QSOP FUNCTION DIP/SO/QSOP TQFN-EP TQFN-EP 1, 15, 16, 15, 14, 13 -- -- A0, A2, A1 Address Inputs -- -- 1, 16 15, 14 A0, A1 Address Inputs 2 16 2 16 EN Enable 3 1 3 1 V- Negative-Supply Voltage Input 4-7 2-5 -- -- NO1-NO14 -- -- 4-7 2-5 NO1A-NO4A Analog Inputs--Bidirectional 8 6 -- -- COM Analog Output--Bidirectional -- -- 8, 9 6, 7 COMA, COMB Analog Outputs--Bidirectional 9-12 7-10 -- -- NO8-NO5 Analog Inputs--Bidirectional -- -- 10-13 8-11 NO4B-NO1B Analog Inputs--Bidirectional 13 11 14 12 V+ Positive-Supply Voltage Input 14 12 15 13 GND -- -- -- -- Exposed Pad Analog Inputs--Bidirectional Ground Exposed Pad (TQFN only). Connect EP to V+. __________Applications Information V+ Operation with Supply Voltages Other than 15V Using supply voltages less than 15V will reduce the analog signal range. The MAX338/MAX339 switches operate with 4.5V to 20V bipolar supplies or with a +4.5V to +30V single supply. Connect V- to GND when operating with a single supply. Both device types can also operate with unbalanced supplies such as +24V and -5V. The Typical Operating Characteristics graphs show typical on-resistance with 20V, 15V, 10V, and 5V supplies. (Switching times increase by a factor of two or more for operation at 5V.) Overvoltage Protection Proper power-supply sequencing is recommended for all CMOS devices. Do not exceed the absolute maximum ratings, because stresses beyond the listed ratings may cause permanent damage to the devices. Always sequence V+ on first, then V-, followed by the logic inputs NO and COM. If power-supply sequencing is not possible, add two small signal diodes in series with supply pins for overvoltage protection (Figure 1). Adding diodes reduces the analog signal range to 1V below V+ and 1V above V-, but does not affect the devices' low switch resistance and low leakage characteristics. Device operation is unchanged, and the difference between V+ and V- should not exceed 44V. 6 NO COM Vg V- Figure 1. Overvoltage Protection Using External Blocking Diodes _______________________________________________________________________________________ 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers +15V V+ 10V NO1 A2 A1 NO2-NO7 A0 MAX338 NO8 EN +10V COM GND VOUT V- LOGIC INPUT 10pF 50 -15V VNO1 V+ SWITCH OUTPUT VOUT 10V NO1B A1 50% 0V 1k +15V 90% 0V A0 90% NO1A-NO4A EN VNO8 NO4B MAX339 +10V tTRANS COMB V- GND tr < 20ns tf < 20ns +3V 50 tTRANS ON VOUT ON 10pF 1k -15V Figure 2. Transition Time +15V V+ EN NO1 -5V NO2-NO8 A0 MAX338 A1 A2 COM GND 50 VOUT V- 10pF 1k LOGIC INPUT V+ NO1B 10% SWITCH OUTPUT VOUT -5V NO1A-NO4A, NO2B-NO4B, COMA 90% VO MAX339 A1 50 tOFF(EN) 0V +15V A0 50% 0V tON(EN) -15V EN tr < 20ns tf < 20ns +3V GND COMB V- VOUT 1k 35pF -15V Figure 3. Enable Switching Time _______________________________________________________________________________________ 7 MAX338/MAX339 ______________________________________________Test Circuits/Timing Diagrams MAX338/MAX339 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers _________________________________Test Circuits/Timing Diagrams (continued) +15V +2.4V V+ EN NO1-NO8 +5V tr < 20ns tf < 20ns +3V LOGIC INPUT 50% 0V A0 A1 VOUT MAX338 80% A2 COM GND SWITCH OUTPUT VOUT V- 10pF tOPEN 0V 1k 50 -15V Figure 4. Break-Before-Make Interval +15V RS V+ NO LOGIC INPUT EN VS CHANNEL SELECT OFF ON OFF 0V A0 COM A1 A2 +3V VOUT MAX338 CL = 100pF GND V- VOUT VOUT VOUT IS THE MEASURED VOLTAGE DUE TO CHARGE TRANSFER ERROR Q WHEN THE CHANNEL TURNS OFF. -15V Q = CL x VOUT Figure 5. Charge Injection 8 _______________________________________________________________________________________ 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers +15V +15V VOUT VIN NO1 RS = 50 V+ COM A1 MAX338 EN 10nF OFF ISOLATION = 20log VOUT RL= 1k NO8 RS = 50 A0 MAX338 COM A1 RL 1k A2 GND V+ NO1 NO2 NO8 A0 10nF 10nF A2 V- GND EN 10nF -15V VOUT CROSSTALK = 20log VIN Figure 6. Off-Isolation V- -15V VOUT VIN Figure 7. Crosstalk +15V V+ NO1 A2 CHANNEL SELECT METER MAX338 A1 NO8 A0 GND EN COM V- IMPEDANCE ANALYZER f = 1MHz -15V Figure 8. NO/COM Capacitance _______________________________________________________________________________________ 9 MAX338/MAX339 _________________________________Test Circuits/Timing Diagrams (continued) MAX338/MAX339 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers ________Pin Configurations/Functional Diagrams/Truth Tables (continued) V+ V- GND TOP VIEW NO1A + 16 A1 NO2A EN 2 15 GND NO3A V- 3 14 V+ NO4A A0 1 MAX339 NO1A 4 13 NO1B NO2A 5 12 NO2B NO3A 6 11 NO3B COMA NO1B NO2B COMB NO3B NO4A 7 10 N04B COMA 8 9 COMB NO4B CMOS DECODE LOGIC DIP/SO/QSOP A1 EN A0 MAX339 DUAL 4-CHANNEL MULTIPLEXER A2 A1 A0 EN ON SWITCH X 0 0 0 0 1 X 0 0 1 1 0 X 0 1 0 1 0 0 1 1 1 1 1 None 1 2 3 4 5 1 0 1 1 6 1 1 1 1 0 1 1 1 7 8 MAX338 A1 A0 EN ON SWITCH X X 0 None 0 0 1 1 0 1 1 2 1 0 1 3 1 1 1 4 MAX339 LOGIC "0" VAL 0.8V, LOGIC "1" VAH 2.4V LOGIC "0" VAL 0.8V, LOGIC "1" VAH 2.4V 10 ______________________________________________________________________________________ 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers TOP VIEW + V- 1 NO1 EN A0 A1 A2 16 15 14 13 + LOGIC 12 GND 2 11 NO2 3 NO3 4 EN A0 A1 GND 16 15 14 13 LOGIC 12 V+ 2 11 NO1B NO2A 3 10 NO2B NO3A 4 9 NO3B V- 1 V+ NO1A 10 NO5 9 NO6 *EP *EP 5 6 7 8 5 6 7 8 NO4 COM NO8 NO7 NO4A COMA COMB NO4B MAX339 TQFN-EP MAX338 TQFN-EP *CONNECT EP TO V+ Ordering Information (continued) PART TEMP RANGE PIN-PACKAGE MAX339EEE+ -40C to +85C 16 QSOP MAX339ETE+ -40C to +85C 16 TQFN-EP** (5mm x 5mm) 16 CERDIP*** MAX339EPE+ -40C to +85C 16 Narrow SO MAX339ESE+ -40C to +85C 16 PDIP 16 Narrow SO -40C to +85C 16 CERDIP TEMP RANGE PIN-PACKAGE MAX338EPE+ -40C to +85C 16 PDIP MAX338ESE+ -40C to +85C 16 Narrow SO MAX338EJE -40C to +85C 16 CERDIP MAX338MJE -55C to +125C MAX338MSE/PR3 -55C to +125C PART MAX339CEE+ 0C to +70C 16 QSOP MAX339EJE MAX339CPE+ 0C to +70C 16 PDIP MAX339MJE -55C to +125C 16 CERDIP*** MAX339CSE+ 0C to +70C 16 Narrow SO MAX339MSE/PR3 -55C to +125C 16 Narrow SO MAX339C/D 0C to +70C Dice* *Contact factory for dice specifications. **EP = Exposed Pad ***Contact factory for availability. +Denotes a lead(Pb)-free/RoHS-compliant package. ______________________________________________________________________________________ 11 MAX338/MAX339 Pin Configurations/Functional Diagrams/Truth Tables (continued) MAX338/MAX339 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers Package Information For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. 12 PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 16 PDIP P16+1 21-0043 -- 16 Narrow SO S16+1 21-0041 90-0097 16 QSOP E16+5 21-0055 90-0167 16 TQFN-EP T1655+3 21-0140 90-0073 16 CDIP J16+4 21-0045 -- ______________________________________________________________________________________ 8-Channel/Dual 4-Channel, Low-Leakage, CMOS Analog Multiplexers REVISION NUMBER REVISION DATE 4 4/12 DESCRIPTION Added the MAX338CEE+ / MAX338EEE+/ MAX338MSE /PR3 / MAX339CEE+ / MAX339EEE+ part and packaging information PAGES CHANGED 1, 2, 6, 10, 11 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. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. 13 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX338/MAX339 Revision History