19-2490; Rev 0; 7/02 KIT ATION EVALU E L B A AVAIL Integrated Temperature Controllers for Peltier Modules ATE PART TEMP RANGE PIN-PACKAGE MAX1978ETM -40°C to +85°C 48 Thin QFN-EP* -40°C to +85°C 48 Thin QFN-EP MAX1979ETM *EP = Exposed pad. MAXIP COMP ITEC 39 37 38 MAXV MAXIN 40 41 42 43 CTLI VDD GND GND 44 45 46 OS1 CS REF 47 TOP VIEW 48 Pin Configuration OS2 1 36 N.C. PGND2 LX2 2 35 3 34 4 33 PGND2 LX2 5 PVDD2 N.C. LX2 PVDD2 SHDN 7 31 MAX1978 MAX1979 30 FREQ N.C. PGND1 LX1 PGND1 LX1 PVDD1 N.C. 24 LX1 PVDD1 GND GND AIN+ AINAOUT 23 25 22 26 12 21 11 20 27 19 28 10 18 29 9 17 8 16 OT 32 6 BFBBFB+ Telecom Fiber Interfaces Ordering Information 15 EDFA Optical Amplifiers ♦ Unipolar +6A Output Current (MAX1979) INTGND DIFOUT FBFB+ Fiber Optic Network Equipment TEC Current Monitor Temperature Monitor Over- and Undertemperature Alarm Bipolar ±3A Output Current (MAX1978) 14 WDM, DWDM Laser-Diode Temperature Control ♦ ♦ ♦ ♦ 13 Fiber Optic Laser Modules ♦ Low-Ripple and Low-Noise Design UT Applications ♦ Circuit Height < 3mm ♦ Temperature Stability to 0.001°C ♦ Integrated Precision Integrator and Chopper Stabilized Op Amps ♦ Accurate, Independent Heating and Cooling Current Limits ♦ Eliminates Surges By Directly Controlling TEC Current ♦ Adjustable Differential TEC Voltage Limit INTOUT A chopper-stabilized instrumentation amplifier and a highprecision integrator amplifier are supplied to create a proportional-integral (PI) or proportional-integral-derivative (PID) controller. The instrumentation amplifier can interface to an external NTC or PTC thermistor, thermocouple, or semiconductor temperature sensor. Analog outputs are provided to monitor TEC temperature and current. In addition, separate overtemperature and undertemperature outputs indicate when the TEC temperature is out of range. An on-chip voltage reference provides bias for a thermistor bridge. The MAX1978/MAX1979 are available in a low-profile 48-lead thin QFN-EP package and is specified over the -40°C to +85°C temperature range. The thermally enhanced QFN-EP package with exposed metal pad minimizes operating junction temperature. An evaluation kit is available to speed designs. Features ♦ Smallest, Safest, Most Accurate Complete Single-Chip Controller ♦ On-Chip Power MOSFETS—No External FETs ♦ Circuit Footprint < 0.93in2 QFN-EP Typical Operating Circuit appears at end of data sheet. *ELECTRICALLY CONNECTED TO THE UNDERSIDE METAL SLUG. NOTE: GND IS CONNECTED TO THE UNDERSIDE METAL SLUG. ________________________________________________________________ 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 MAX1978/MAX1979 General Description The MAX1978/MAX1979 are the smallest, safest, most accurate complete single-chip temperature controllers for Peltier thermoelectric cooler (TEC) modules. On-chip power FETs and thermal control-loop circuitry minimize external components while maintaining high efficiency. Selectable 500kHz/1MHz switching frequency and a unique ripple-cancellation scheme optimize component size and efficiency while reducing noise. Switching speeds of internal MOSFETs are optimized to reduce noise and EMI. An ultralow-drift chopper amplifier maintains ±0.001°C temperature stability. Output current, rather than voltage, is directly controlled to eliminate current surges. Individual heating and cooling current and voltage limits provide the highest level of TEC protection. The MAX1978 operates from a single supply and provides bipolar ±3A output by biasing the TEC between the outputs of two synchronous buck regulators. True bipolar operation controls temperature without “dead zones” or other nonlinearities at low load currents. The control system does not hunt when the set point is very close to the natural operating point, where only a small amount of heating or cooling is needed. An analog control signal precisely sets the TEC current. The MAX1979 provides unipolar output up to 6A. MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V SHDN, MAXV, MAXIP, MAXIN, CTLI, OT, UT to GND............................................-0.3V to +6V FREQ, COMP, OS1, OS2, CS, REF, ITEC, AIN+, AIN-, AOUT, INT-, INTOUT, BFB+, BFB-, FB+, FB-, DIFOUT to GND......................................-0.3V to (VDD + 0.3V) PVDD1, PVDD2 to VDD ...........................................-0.3V to +0.3V PVDD1, PVDD2 to GND...............................-0.3V to (VDD + 0.3V) PGND1, PGND2 to GND .......................................-0.3V to +0.3V COMP, REF, ITEC, OT, UT, INTOUT, DIFOUT, BFB-, BFB+, AOUT Short to GND .............................Indefinite Peak LX Current (MAX1978) (Note 1).................................±4.5A Peak LX Current (MAX1979) (Note 1)....................................+9A Continuous Power Dissipation (TA = +70°C) 48-Lead Thin QFN-EP (derate 26.3mW/°C above +70°C) (Note 2) .................2.105W Operating Temperature Ranges MAX1978ETM ..................................................-40°C to +85°C MAX1979ETM ..................................................-40°C to +85°C Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: LX has internal clamp diodes to PGND and PVDD. Applications that forward bias these diodes should not exceed the IC’s package power dissipation limits. Note 2: Solder underside metal slug to PC board ground plane. 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 (VDD = PVDD1 = PVDD2 = SHDN = 5V, FREQ = GND, CTLI = FB+ = FB- = MAXV = MAXIP = MAXIN = REF, TA = 0°C to +85°C, unless otherwise noted. Typical values at TA = +25°C.) PARAMETER Input Supply Range SYMBOL CONDITIONS VDD VDD = 5V, ITEC = 0 to ±3A, VOUT = VOS1 - VOS2 (MAX1978) Output Voltage Range Maximum TEC Current Reference Voltage Reference Load Regulation VOUT ITEC(MAX) VREF ∆VREF VDD = 3V, ITEC = 0 to ±3A, VOUT = VOS1 - VOS2 (MAX1978) RDS(ON-P) NFET Leakage 2 ILEAK(N) UNITS 3.0 5.5 V -4.3 +4.3 4.3 V -2.3 +2.3 2.3 MAX1978 ±3 MAX1979 6 VDD = 3V to 5.5V, IREF = 150µA 1.485 VDD = 3V to 5.5V, IREF = +10µA to -1mA VOS1 > VCS PFET On-Resistance MAX VDD = 3V, ITEC = 0 to 6A, VOUT = VOS1 (MAX1979) Current-Sense Threshold RDS(ON-N) TYP VDD = 5V, ITEC = 0 to 6A, VOUT = VOS1 (MAX1979) VOS1 < VCS NFET On-Resistance MIN A 1.500 1.515 V 1.2 5 mV 160 VMAXI_ = VREF 135 150 VMAXI_ = VREF/3 40 50 60 VMAXI_ = VREF 135 150 160 VMAXI_ = VREF/3 40 50 60 VDD = 5V, I = 0.5A 0.04 0.07 VDD = 3V, I = 0.5A 0.06 0.08 VDD = 5V, I = 0.5A 0.06 0.10 VDD = 3V, I = 0.5A 0.09 0.12 VLX = VDD = 5V, TA = +25°C 0.02 10 VLX = VDD = 5V, TA = +85°C 1 _______________________________________________________________________________________ mV Ω Ω µA Integrated Temperature Controllers for Peltier Modules (VDD = PVDD1 = PVDD2 = SHDN = 5V, FREQ = GND, CTLI = FB+ = FB- = MAXV = MAXIP = MAXIN = REF, TA = 0°C to +85°C, unless otherwise noted. Typical values at TA = +25°C.) PARAMETER PFET Leakage SYMBOL TYP MAX VLX = 0, TA = +25°C 0.02 10 VLX = 0, TA = +85°C 1 IDD(NO VDD = 5V 30 50 LOAD) VDD = 3.3V 15 30 IDD-SD SHDN = GND, VDD = 5V (Note 3) 2 3 ILEAK(P) No-Load Supply Current Shutdown Supply Current Thermal Shutdown CONDITIONS MIN TSHUTDOWN Hysteresis = 15°C 165 UNITS µA mA mA °C VDD rising 2.4 2.6 2.8 VDD falling 2.25 2.5 2.75 FREQ = GND 450 500 650 FREQ=VDD 800 1000 1200 UVLO Threshold VUVLO Switching Frequency Internal Oscillator fSW-INT OS1, OS2, CS Input Current IOS1, IOS2, ICS 0 or VDD -100 +100 µA SHDN, FREQ Input Current ISHDN, IFREQ 0 or VDD -5 +5 µA 0.25 × VDD V SHDN, FREQ Input Low Voltage VIL VDD = 3V to 5.5V SHDN, FREQ Input High Voltage VIH VDD = 3V to 5.5V MAXV Threshold Accuracy MAXV, MAXIP, MAXIN Input Bias Current 0.75 × VDD kHz V VMAXV = VREF ✕ 0.67, VOS1 to VOS2 = ±4V, VDD = 5V -1 +1 VMAXV = VREF ✕ 0.33, VOS1 to VOS2 = ±2V, VDD = 3V -2 +2 -0.1 +0.1 IMAXV-BIAS, VMAXV = VMAXI_ = 0.1V or 1.5V IMAXI_-BIAS V % µA CTLI Gain ACTLI VCTLI = 0.5V to 2.5V (Note 4) 9.5 10 10.5 V/V CTLI Input Resistance RCTLI 1MΩ terminated at REF 0.5 1.0 2.0 MΩ 50 100 175 µS Error Amp Transconductance gm ITEC Accuracy VOS1 to VCS = +100mV or -100mV -10 +10 % ITEC Load Regulation VOS1 to VCS = +100mV or -100mV, IITEC = ±10µA -0.1 +0.1 % ∆VITEC Instrumentation Amp Input Bias Current IDIF-BIAS Instrumentation Amp Offset Voltage VDIF-OS Instrumentation Amp OffsetVoltage Drift with Temperature Instrumentation Amp Preset Gain VDD = 3V to 5.5V -10 0 +10 nA -200 +20 +200 µV VDD = 3V to 5.5V ADIF RLOAD = 10kΩ to REF 0.1 45 50 µV/°C 55 V/V _______________________________________________________________________________________ 3 MAX1978/MAX1979 ELECTRICAL CHARACTERISTICS (continued) MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules ELECTRICAL CHARACTERISTICS (continued) (VDD = PVDD1 = PVDD2 = SHDN = 5V, FREQ = GND, CTLI = FB+ = FB- = MAXV = MAXIP = MAXIN = REF, TA = 0°C to +85°C, unless otherwise noted. Typical values at TA = +25°C.) PARAMETER Integrator Amp Open-Loop Gain SYMBOL AOL-INT CONDITIONS MIN RLOAD = 10kΩ to REF TYP MAX UNITS 120 dB 100 dB Integrator Amp CMRR CMRRINT Integrator Amp Input Bias Current IINT-BIAS VDD = 3V to 5.5V Integrator Amp Voltage Offset VINT-OS VDD = 3V to 5.5V Integrator Amp Gain Bandwidth GBWINT Undedicated Chopper Amp Open-Loop Gain AOL-AIN Undedicated Chopper Amp CMRR CMRRAIN Undedicated Chopper Amp Input Bias Current IAIN-BIAS VDD = 3V to 5.5V -10 0 +10 nA Undedicated Chopper Amp Offset Voltage VAIN-OS VDD = 3V to 5.5V -200 +10 +200 µV Undedicated Chopper Amp Gain Bandwidth GBWAIN Undedicated Chopper Amp Output Ripple VRIPPLE BFB_ Buffer Error -3 RLOAD = 10kΩ to REF A=5 nA mV 100 kHz 120 dB 85 dB 100 kHz 20 mV +200 1 µA Sinking 4mA 50 150 mV UT Trip Threshold FB+ - FB- (see Typical Application Circuit) -20 mV OT Trip Threshold FB+ - FB- (see Typical Application Circuit) 20 mV UT and OT Output Low Voltage 4 ILEAK VOL -200 1 +3 0 UT and OT Leakage Current CLOAD < 100pF +0.1 V UT = V OT = 5.5V _______________________________________________________________________________________ µV Integrated Temperature Controllers for Peltier Modules (VDD = PVDD1 = PVDD2 = SHDN = 5V, FREQ = GND, CTLI = FB+ = FB- = MAXV = MAXIP = MAXIN = REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 5) PARAMETER Input Supply Range SYMBOL CONDITIONS VDD VDD = 5V, ITEC = 0 to ±3A, VOUT = VOS1 -VOS2 (MAX1978) Output Voltage Range Maximum TEC Current Reference Voltage VOUT ITEC(MAX) VREF Reference Load Regulation ∆VREF VDD = 3V, ITEC = 0 to ±3A, VOUT = VOS1 - VOS2 (MAX1978) -4.3 +4.3 4.3 V -2.3 +2.3 MAX1978 ±3 MAX1979 6 VDD = 3V to 5.5V, IREF = 150µA 1.475 VDD = 3V to 5.5V, IREF = 10µA to -1mA V 5 mV VMAXI_ = VREF 135 VMAXI_ = VREF/3 40 160 60 VMAXI_ = VREF 135 160 VMAXI_ = VREF/3 40 60 VDD = 5V 50 LOAD) VDD = 3.3V 30 IDD-SD SHDN = GND, VDD = 5V (Note 3) VUVLO Switching Frequency Internal Oscillator fSW-INT 3 mV mA mA VDD rising 2.4 2.8 VDD falling 2.25 2.75 FREQ = GND 450 650 FREQ = VDD 800 1200 -100 +100 µA -5 +5 µA 0.25 ✕ VDD V IOS1, IOS2, 0 or VDD ICS I SHDN, I FREQ A 1.515 IDD(NO UVLO Threshold SHDN, FREQ Input Current V 2.3 VOS1 > VCS OS1, OS2, CS Input Current UNITS 5.5 VDD = 3V, ITEC = 0 to 6A, VOUT = VOS1 (MAX1979) Current-Sense Threshold Shutdown Supply Current MAX 3 VDD = 5V, ITEC = 0 to 6A, VOUT = VOS1 (MAX1979) VOS1 < VCS No-Load Supply Current MIN 0 or VDD SHDN, FREQ Input Low Voltage VIL VDD = 3V to 5.5V SHDN, FREQ Input High Voltage VIH VDD = 3V to 5.5V 0.75 ✕ VDD V kHz V _______________________________________________________________________________________ 5 MAX1978/MAX1979 ELECTRICAL CHARACTERISTICS MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules ELECTRICAL CHARACTERISTICS (continued) (VDD = PVDD1 = PVDD2 = SHDN = 5V, FREQ = GND, CTLI = FB+ = FB- = MAXV = MAXIP = MAXIN = REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 5) PARAMETER SYMBOL MAXV Threshold Accuracy MAXV, MAXIP, MAXIN Input Bias Current CONDITIONS MIN MAX VMAXV = VREF ✕ 0.67, VOS1 to VOS2 = ±4V, VDD = 5V -1 +1 VMAXV = VREF ✕ 0.33, VOS1 to VOS2 = ±2V, VDD = 3V -2 +2 -0.1 +0.1 IMAXV-BIAS, VMAXV = VMAXI_ = 0.1V or 1.5V IMAXI_-BIAS UNITS % µA CTLI Gain ACTLI VCTLI = 0.5V to 2.5V (Note 4) 9.5 10.5 V/V CTLI Input Resistance RCTLI 1MΩ terminated at REF 0.5 2.0 MΩ 50 175 µS -10 +10 % -0.125 +0.125 % -10 +10 nA -200 +200 µV 45 55 V/V Error Amp Transconductance gm ITEC Accuracy VOS1 to VCS = +100mV or -100mV ITEC Load Regulation ∆VITEC Instrumentation Amp Input Bias Current IDIF-BIAS Instrumentation Amp Offset Voltage VDIF-OS Instrumentation Amp Preset Gain ADIF VOS1 to VCS = +100mV or -100mV, IITEC = ±10µA VDD = 3V to 5.5V RLOAD = 10kΩ to REF Integrator Amp Input Bias Current IINT-BIAS VDD = 3V to 5.5V 1 nA Integrator Amp Voltage Offset VINT-OS VDD = 3V to 5.5V -3 +3 mV Undedicated Chopper Amp Input Bias Current IAIN-BIAS VDD = 3V to 5.5V -10 +10 nA Undedicated Chopper Amp Offset Voltage VAIN-OS VDD = 3V to 5.5V -200 +200 µV CLOAD < 100pF -200 +200 µV 1 µA 150 mV BFB_ Buffer Error UT and OT Leakage Current UT and OT Output Low Voltage ILEAK VOL V UT = V OT = 5.5V Sinking 4mA Note 3: Includes power FET leakage. Note 4: CTLI gain is defined as: A CTLI = (VCTLI −VREF ) (VOSI −VCS ) Note 5: Specifications to -40°C are guaranteed by design, not production tested. 6 _______________________________________________________________________________________ Integrated Temperature Controllers for Peltier Modules EFFICIENCY vs. TEC CURRENT VDD = 5V EFFICIENCY vs. TEC CURRENT VDD = 3.3V 70 60 EFFICIENCY (%) 60 50 40 30 VOS1 100mV/div AC-COUPLED 40 30 VOS1 - VOS1 50mV/div RTEC = 0.855Ω RTEC = 1.1Ω 10 10 0 VOS2 100mV/div AC-COUPLED 50 20 20 MAX1978 toc03 70 MAX1978 toc02 80 0 0.5 1.0 1.5 2.0 2.5 0 0.5 1.0 1.5 2.5 2.0 TEC CURRENT (A) TEC CURRENT (A) INPUT SUPPLY RIPPLE TEC CURRENT vs. CTLI VOLTAGE 400ns/div ZERO-CROSSING TEC CURRENT MAX1978 toc05 MAX1978 toc04 0 MAX1978 toc06 EFFICIENCY (%) 80 MAX1978 toc01 90 OUTPUT-VOLTAGE RIPPLE WAVEFORMS VCTLI 200mV/div 1.5V VCTLI 1V/div VDD 20mV/div AC-COUPLED -0V -0A 1ms/div VITEC vs. TEC CURRENT TEC CURRENT vs. TEMPERATURE SWITCHING FREQUENCY vs. TEMPERATURE 1.005 ITEC (A) 1.5 1.000 1.0 0.995 0.5 ITEC = 1A RSENSE = 0.68Ω 0 0.990 -1 0 1 TEC CURRENT (A) 2 3 MAX1978 toc09 508 506 SWITCHING FREQUENCY (kHz) MAX1978 toc08 MAX1978 toc07 1.010 2.0 VITEC (V) 0A 20ms/div 2.5 -2 ITEC 500mA/div 200ns/div 3.0 -3 ITEC 2A/div 504 502 500 498 496 VCTLI = 1.5V RTEC = 1Ω 494 492 -40 -20 0 20 40 TEMPERATURE (°C) 60 80 -40 -20 0 20 40 60 80 TEMPERATURE (°C) _______________________________________________________________________________________ 7 MAX1978/MAX1979 Typical Operating Characteristics (VDD = 5V, VCTLI = 1V, VFREQ = GND, RTEC = 1Ω, circuit of Figure 1, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VDD = 5V, VCTLI = 1V, VFREQ = GND, RTEC = 1Ω, circuit of Figure 1, TA = +25°C, unless otherwise noted.) REFERENCE VOLTAGE CHANGE vs. INPUT SUPPLY 0 -5 -10 -15 -20 -25 -30 0.5 0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -35 3.5 3.0 4.0 4.5 5.0 1 0 -1 -2 -3 3.5 4.0 4.5 5.0 5.5 -40 -20 0 20 60 80 TEMPERATURE (°C) REFERENCE LOAD REGULATION ATO VOLTAGE vs. THERMISTOR TEMPERATURE STARTUP AND SHUTDOWN WAVEFORMS MAX1978 toc14 MAX1978 toc13 4.5 NTC, 10kΩ THERMISTOR CIRCUIT IN FIGURES 1 AND 2 4.0 3.5 ATO VOLTAGE (V) 0.2 0 -0.2 -0.4 SINK SOURCE MAX1978 toc15 VDD (V) 0.4 VSHDN 5V/div 3.0 2.5 ITEC 500mA/div 2.0 1.5 1.0 -0.8 IDD 200mA/div 0.5 -1.0 0 0 0.2 0.4 0.6 0.8 1.0 -10 0 10 20 30 40 50 THERMISTOR TEMPERATURE (°C) CTLI STEP RESPONSE INPUT SUPPLY STEP RESPONSE VCTLI 1V/div 60 100µs/div THERMAL STABILITY, COOLING MODE MAX1978 toc17 REFERENCE LOAD CURRENT (mA) MAX1978 toc18 -0.2 MAX1978 toc16 -0.4 VDD 2V/div 1.5V ITEC 1A/div 0V ITEC 20mA/div TEMPERATURE 0.001°C/div 0A 1A 1ms/div 8 40 VDD (V) 0.6 -0.6 2 -4 3.0 5.5 3 MAX1978 toc12 1.0 MAX1978 toc11 5 REFERENCE VOLTAGE CHANGE (mV) MAX1978 toc10 SWITCHING FREQUENCY CHANGE (kHz) 10 REFERENCE VOLTAGE CHANGE vs. TEMPERATURE REFERENCE VOLTAGE CHANGE (mV) SWITCHING FREQUENCY CHANGE vs. INPUT SUPPLY REFERENCE VOLTAGE CHANGE (mV) MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules ITEC = +25°C TA = +45°C 10ms/div _______________________________________________________________________________________ 4s/div Integrated Temperature Controllers for Peltier Modules TEMPERATURE 0.001°C/div ITEC = +25°C TA = +25°C TTEC = +25°C TA = +5°C MAX1978 toc21 MAX1978 toc20 0.03 0.02 TEMPERATURE ERROR (°C) TEMPERATURE 0.001°C/div TEMPERATURE ERROR vs. AMBIENT TEMPERATURE THERMAL STABILITY, HEATING MODE MAX1978 toc19 THERMAL STABILITY, ROOM TEMPERATURE 0.01 0 -0.01 -0.02 -0.03 4s/div 4s/div -20 -10 0 10 20 30 40 50 AMBIENT TEMPERATURE (°C) Pin Description PIN NAME FUNCTION 1 OS2 Output Sense 2. OS2 senses one side of the differential TEC voltage. OS2 is a sense point, not a power output. 2, 8, 29, 35 N.C. Not Internally Connected 3, 5 PGND2 4, 6, 9 LX2 7, 10 PVDD2 11 SHDN Power Ground 2. Internal synchronous rectifier ground connections. Connect all PGND pins together at power ground plane. Inductor 2 Connection. Connect all LX2 pins together. Connect LX2 to LX1 when using the MAX1979. Power 2 Inputs. Must be same voltage as VDD. Connect all PVDD2 inputs together at the VDD power plane. Bypass to PGND2 with a 10µF ceramic capacitor. Shutdown Control Input. Active-low shutdown control. 12 OT Under-Temperature Alarm. Open-drain output pulls low if temperature feedback falls 20mV (typically +1.5°C) below the set-point voltage. 13 UT Under-Temperature Alarm. Open-drain output pulls low if temperature feedback falls 20mV (typically +1.5°C) below the set-point voltage. 14 INTOUT Integrator Amp Output. Normally connected to CTLI. 15 INT- Integrator Amp Inverting Input. Normally connected to DIFOUT through thermal-compensation network. 16, 25, 26, 42, 43 GND Analog Ground. Connect all GND pins to analog ground plane. 17 DIFOUT Chopper-Stabilized Instrumentation Amp Output. Differential gain is 50 ✕ (FB+ - FB-). 18 FB- Chopper-Stabilized Instrumentation Amp Inverting Input. Connect to thermistor bridge. 19 FB+ Chopper-Stabilized Instrumentation Amp Noninverting Input. Connect to thermistor bridge. 20 BFB- Chopper-Stabilized Buffered FB- Output. Used to monitor thermistor bridge voltage. 21 BFB+ Chopper-Stabilized Buffered FB+ Output. Used to monitor thermistor bridge voltage. 22 AIN+ Undedicated Chopper-Stabilized Amplifier Noninverting Input _______________________________________________________________________________________ 9 MAX1978/MAX1979 Typical Operating Characteristics (continued) (VDD = 5V, VCTLI = 1V, VFREQ = GND, RTEC = 1Ω, circuit of Figure 1, TA = +25°C, unless otherwise noted.) MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules Pin Description (continued) PIN NAME 23 AIN- 24 AOUT Undedicated Chopper-Stabilized Amplifier Output 27, 30 PVDD1 Power 1 Inputs. Must be same voltage as VDD. Connect all PVDD1 inputs together at the VDD power plane. Bypass to PGND1 with a 10µF ceramic capacitor. 28, 31, 33 LX1 Inductor 1 Connection. Connect all LX1 pins together. Connect LX1 to LX2 when using the MAX1979. Power Ground 1. Internal synchronous-rectifier ground connections. Connect all PGND pins together at power ground plane. 32, 34 PGND1 36 FREQ Switching-Frequency Select. Low = 500kHz, high = 1MHz. ITEC TEC Current Monitor Output. The ITEC output voltage is a function of the voltage across the TEC currentsense resistor. VITEC = 1.50V + (VOS1 - VCS) ✕ 8. 37 10 FUNCTION Undedicated Chopper-Stabilized Amplifier Inverting Input 38 COMP Current-Control Loop Compensation. For most designs, connect a 10nF capacitor from COMP to GND. 39 MAXIP Maximum Positive TEC Current. Connect MAXIP to REF to set default positive current limit +150mV / RSENSE. 40 MAXIN Maximum Negative TEC Current. Connect MAXIN to REF to set default negative current limit -150mV / RSENSE. Connect MAXIN to GND when using the MAX1979. 41 MAXV Maximum Bipolar TEC Voltage. Connect an external resistive divider from REF to GND to set the maximum voltage across the TEC. The maximum TEC voltage is 4 ✕ VMAXV. 44 VDD Analog Supply Voltage Input. Bypass to GND with a 10µF ceramic capacitor. 45 CTLI TEC Current-Control Input. Sets differential current into the TEC. Center point is 1.50V (no TEC current). Connect to INTOUT when using the thermal control loop. ITEC = (VOS1 - VCS) / RSENSE = (VCTLI - 1.50) / (10 ✕ RSENSE). When (VCLTI - VREF) > 0, VOS2 > VOS1 > VCS. 46 REF 1.5V Reference Voltage Output. Bypass REF to GND with a 1µF ceramic capacitor. 47 CS Current-Sense Input. The current through the TEC is monitored between CS and OS1. The maximum TEC current is given by 150mV / RSENSE and is bipolar for the MAX1978. The MAX1979 TEC current is unipolar. 48 OS1 Output Sense 1. OS1 senses one side of the differential TEC voltage. OS1 is a sense point, not a power output. ______________________________________________________________________________________ Integrated Temperature Controllers for Peltier Modules ON OFF SHDN FREQ VDD REF 1.5V REFERENCE MAXV PVDD1 MAX VTEC = VMAXV x 4 MAXIP 3V TO 5.5V LX1 MAX ITEC = (VMAXIP/ VREF) x (0.15V/RSENSE) MAX ITEC = (VMAXIN/ VREF) x (0.15V/RSENSE) MAXIN CS ITEC PWM CONTROL AND GATE DRIVE PGND1 CS RSENSE OS1 OS1 OS2 REF PVDD2 CTLI VDD COMP LX2 MAX1978 GND OT PGND2 50R REF + 1V R UT REF 50R R REF - 1V REF BFB- BFB+ INTOUT INT- AIN- AOUT AIN+ DIFOUT FB+ FB- ______________________________________________________________________________________ 11 MAX1978/MAX1979 Functional Diagram MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules TEC temperature. The on-chip thermal-control circuitry can be configured to achieve temperature control stability of 0.001°C. Figure 1 shows a typical TEC thermalcontrol circuit. Detailed Description Power Stage The power stage of the MAX1978/MAX1979 thermoelectric cooler (TEC) temperature controllers consists of two switching buck regulators that operate together to directly control TEC current. This configuration creates a differential voltage across the TEC, allowing bidirectional TEC current for controlled cooling and heating. Controlled cooling and heating allow accurate TEC temperature control within the tight tolerances of laser driver specifications. Ripple Cancellation Switching regulators like those used in the MAX1978/MAX1979 inherently create ripple voltage on each common-mode output. The regulators in the MAX1978 switch in phase and provide complementary in-phase duty cycles, so ripple waveforms at the differential TEC output are greatly reduced. This feature suppresses ripple currents and electrical noise at the TEC to prevent interference with the laser diode while minimizing output capacitor filter size. The voltage at CTLI directly sets the TEC current. The internal thermal-control loop drives CTLI to regulate VDD REF 10µF 10µF 1µF 10µF 0.01µF VDD SHDN PVDD1 PVDD2 REF MAXV MAXIN MAXIP COMP UNDERTEMP ALARM OVERTEMP ALARM DC CURRENT MONITOR 3µH LX1 CS UT 1µF 0.068Ω OT OS1 ITEC 20kΩ 1% 4.7µF MAX1978 TEC BFB80.6kΩ 1µF THERMISTOR VOLTAGE MONITOR AIN- OS2 AOUT 3µH LX2 1µF AIN+ REF 69.8kΩ 1% 105kΩ 1% CTLI FREQ GND REF PGND2 PGND1 INTOUT FBDIFOUT FB+ INT- 10kΩ 100kΩ 100kΩ 0.047µF 10µF 0.47µF 20kΩ 1MΩ Figure 1. MAX1978 Typical Application Circuit 12 ______________________________________________________________________________________ THERMAL FEEDBACK Integrated Temperature Controllers for Peltier Modules Voltage and Current-Limit Settings The MAX1978 and MAX1979 provide settings to limit the maximum differential TEC voltage. Applying a voltage to MAXV limits the maximum voltage across the TEC to ±(4 ✕ VMAXV). The MAX1978 also limits the maximum positive and negative TEC current. The voltages applied to MAXIP and MAXIN independently set the maximum positive and negative output current limits. The MAX1979 controls TEC current in only one direction, so the maximum current is set only with MAXIP. MAXIN must be connected to GND when using the MAX1979. Chopper-Stabilized Instrumentation Amplifier The MAX1978 and MAX1979 include a chopped input instrumentation amplifier with a fixed gain of 50. An external thermal sensor, typically a thermistor, is connected to one of the amp’s inputs. The other input is connected to a voltage that represents the temperature set point. This set point can be derived from a resistordivider network or DAC. The included instrumentation amplifier provides low offset drift needed to prevent temperature set-point drift with ambient temperature changes. Temperature stability of 0.001°C can be achieved over a 0°C to +50°C ambient temperarure range by using the amplifier as in Figure 1. DIFOUT is the instrumentation amplifier output and is proportional to 50 times the difference between the set-point temperature and the TEC temperature. This difference is commonly referred to as the “error signal”. For best temperature stability, derive the set-point voltage from the same reference that drives the thermistor (usually the MAX1978/MAX1979 REF output). This is called a “ratiometric” or “bridge” connection. The bridge connection optimizes stability by eliminating REF drift as an error source. Errors at REF are nullified because they affect the thermistor and set point equally. The instrumentation amplifier utilizes a chopped input scheme to minimize input offset voltage and drift. This generates output ripple at DIFOUT that is equal to the chop frequency. The DIFOUT peak-to-peak ripple amplitude is typically 100mV but has no effect on temperature stability. DIFOUT ripple is filtered by the integrator in the following stage. The chopper frequency is derived from, and is synchronized to, the switching frequency of the power stage. Integrator Amplifier An on-chip integrator amplifier is provided on the MAX1978/MAX1979. The noninverting terminal of the amplifier is connected internally to REF. Connect an appropriate network of resistors and capacitors between DIFOUT and INT-, and connect INTOUT to CTLI for typical operation. CTLI directly controls the TEC current magnitude and polarity. The thermal-control-loop dynamics are set by the integrator input and feedback components. See the Applications Information section for details on thermal-loop compensation. Current Monitor Output ITEC provides a voltage output proportional to the TEC current, ITEC (see the Functional Diagram): VITEC = 1.5V + 8 ✕ (VOS1 - VCS) Over- and Under-Temperature Alarms The MAX1978/MAX1979 provide open-drain status outputs that alert a microcontroller when the TEC temperature is over or under the set-point temperature. OT and UT pull low when V(FB1+ - FB-) is more than 20mV. For a typical thermistor connection, this translates to approximately 1.5°C error. Reference Output The MAX1978/MAX1979 include an on-chip 1.5V voltage reference accurate to 1% over temperature. Bypass REF with 1µF to GND. REF can be used to bias an external thermistor for temperature sensing as shown in Figures 1 and 2. Note that the 1% accuracy of REF does not limit the temperature stability achievable with the MAX1978/MAX1979. This is because the thermistor and set-point bridge legs are intended to be driven ratiometrically by the same reference source (REF). Variations in the bridge-drive voltage then cancel out and do not generate errors. Consequently, 0.001°C stable temperature control is achievable with the MAX1978/MAX1979 reference. An external source can be used to bias the thermistor bridge. For best accuracy, the common-mode voltage applied to FB+ and FB- should be kept between 0.5V and 1V, however the input range can be extended from 0.2V to VDD / 2 if some shift in instrumentation amp offset (approximately -50µV/V) can be tolerated. This shift remains constant with temperature and does not contribute to set-point drift. ______________________________________________________________________________________ 13 MAX1978/MAX1979 Switching Frequency FREQ sets the switching frequency of the internal oscillator. The oscillator frequency is 500kHz when FREQ = GND. The oscillator frequency is 1MHz when FREQ = VDD. The 1MHz setting allows minimum inductor and filter-capacitor values. Efficiency is optimized with the 500kHz setting. MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules VDD REF 10µF 10µF 1µF 10µF 0.01µF VDD SHDN PVDD1 PVDD2 COMP UNDERTEMP ALARM OVERTEMP ALARM DC CURRENT MONITOR UT REF MAXV MAXIN MAXIP LX1 LX2 CS 3µH 1µF OT 0.03Ω ITEC OS1 20kΩ 1% MAX1979 4.7µF BFB80.6kΩ 1µF THERMISTOR VOLTAGE MONITOR AIN- TEC OS2 AOUT AIN+ REF 69.8kΩ 1% 105kΩ 1% CTLI FREQ GND FB- REF THERMAL FEEDBACK FB+ PGND2 PGND1 INTOUT INT- DIFOUT 10kΩ 100kΩ 10µF 0.047µF 0.47µF 20kΩ 100kΩ 1MΩ Figure 2. MAX1979 Typical Application Circuit Buffered Outputs, BFB+ and BFBBFB+ and BFB- output a buffered version of the voltage that appears on FB+ and FB-, respectively. The buffers are typically used in conjunction with the undedicated chopper amplifier to create a monitor for the thermistor voltage/TEC temperature (Figures 1 and 2). These buffers are unity-gain chopper amplifiers and exhibit output ripple. Each output can be either integrated or filtered to remove the ripple content if necessary. tional analog output. The thermistor voltage typically is connected to the undedicated chopper amplifier through the included buffers BFB+ and BFB-. Figure 3 shows how to configure the undedicated amplifier as a thermistor voltage monitor. The output voltage at AOUT is not precisely linear, because the thermistor is not linear. AOUT is also chopper stabilized and exhibits output ripple and can be either integrated or filtered to remove the ripple content if necessary. Undedicated Chopper-Stabilized Amplifier In addition to the chopper amplifiers at DIFOUT and BFB_, the MAX1978/MAX1979 include an additional chopper amplifier at AOUT. This amplifier is uncommitted but is intended to provide a temperature-propor14 ______________________________________________________________________________________ Integrated Temperature Controllers for Peltier Modules 69.8kΩ 1% Compensation Capacitor Include a compensation capacitor to ensure currentpower control-loop stability. Select the capacitor so that the unity-gain bandwidth of the current-control loop is less than or equal to 10% the resonant frequency of the output filter: AIN+ 105kΩ 1% AOUT 80.6kΩ 1% 1µF g 24 × RSENSE CCOMP ≥ m × fBW 2π × (RSENSE + RTEC ) AINREF MAX1978 MAX1979 x50 20kΩ 1% BFB- 10kΩ where: fBW = unity-gain bandwidth frequency gm = loop transconductance, typically 100µA/V CCOMP = value of the compensation capacitor FBVSETPOINT FB+ RTEC = TEC series resistance RSENSE = sense resistor Setting Voltage and Current Limits Figure 3. Thermistor Voltage Monitor Design Procedure Inductor Selection Small surface-mount inductors are ideal for use with the MAX1978/MAX1979. Select the output inductors so that the LC resonant frequency of the inductance and the output capacitance is less than 1/5 the selected switching frequency. For example, 3.0µH and 1µF have a resonance at 92kHz, which is adequate for 500kHz operation. ¡ f LC= 1 2π LC where: fLC = resonant frequency of output filter. Capacitor Selection Filter Capacitors Decouple each power-supply input (VDD, PVDD1, and PVDD2) with a 10µF ceramic capacitor close to the supply pins. If long supply lines separate the source supply from the MAX1978/MAX1979, or if the source supply has high output impedance, place an additional Consider TEC parameters to guarantee a robust design. These parameters include maximum positive current, maximum negative current, and the maximum voltage allowed across the TEC. These limits should be used to set MAXIP, MAXIN, and MAXV voltages. Setting Max Positive and Negative TEC Current MAXIP and MAXIN set the maximum positive and negative TEC currents, respectively. The default current limit is ±150mV / RSENSE when MAXIP and MAXIN are connected to REF. To set maximum limits other than the defaults, connect a resistor-divider from REF to GND to set VMAXI_. Use resistors in the 10kΩ to 100kΩ range. VMAXI_ is related to ITEC by the following equations: VMAXIP = 10 (ITECP(MAX) ✕ RSENSE) VMAXIN = 10 (ITECN(MAX) ✕ RSENSE) where ITECP(MAX) is the maximum positive TEC current and ITECN(MAX) is the maximum negative TEC current. Positive TEC current occurs when CS is less than OS1: ITEC ✕ RSENSE = CS - OS1 when ITEC < 0. ITEC ✕ RSENSE = OS1 - CS when ITEC > 0. ______________________________________________________________________________________ 15 MAX1978/MAX1979 22µF to 100µF ceramic capacitor between the V DD power plane and power ground. Insufficient supply bypassing can result in supply bounce and degraded accuracy. REF MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules The MAX1979 controls the TEC current in only one direction (unipolar). Set the maximum unipolar TEC current by applying a voltage to MAXIP. Connect MAXIN to GND when using the MAX1979. The equation for setting MAXIP is the same for the MAX1978 and MAX1979. Do not exceed the positive or negative current-limit specifications on the TEC. Refer to the TEC manufacturer’s data sheet for these limits. FBREF CREF MAX1978 MAX1979 FB+ VTHERMISTOR VSETPOINT Setting Max TEC Voltage Apply a voltage to MAXV to control the maximum differential TEC voltage. MAXV can vary from 0 to REF. The voltage across the TEC is four times VMAXV and can be positive or negative. FBREF |VOS1 - VOS2| = 4 ✕ VMAXV Use resistors from 10kΩ to 100kΩ to form a voltagedivider to set VMAXV. Thermal-Control Loop The MAX1978/MAX1979 provide all the necessary amplifiers needed to create a thermal-control loop. Typically, the chopper-stabilized instrumentation amplifier generates an error signal and the integrator amplifier is used to create a PID controller. Figure 4 shows an example of a simple PID implementation. The error signal needed to control the loop is generated from the difference between the set point and the thermistor voltage. The desired set-point voltage can be derived from a potentiometer, DAC, or other voltage source. Figure 5 details the required connections. Connect the output of the PID controller to CTLI. For details, see the Applications Information section. VTHERMISTOR CREF MAX1978 MAX1979 FB+ DAC VSETPOINT DIGITAL INPUT Figure 5. The Set Point can be Derived from a Potentiometer or a DAC Control Inputs/Outputs TEC Current Control The voltage at CTLI directly sets the TEC current. CTLI typically is driven from the output of a temperature-control circuit CINTOUT. For the purposes of the following equations, it is assumed that positive TEC current is heating. The transfer function relating current through the TEC (ITEC) and VCTLI is given by: C3 ITEC = (VCTLI - VREF) / (10 ✕ RSENSE) C1 R3 R1 C2 INT- DIFOUT INTOUT R2 where VREF is 1.50V and ITEC = (VOS1 - VCS) / RSENSE VCTLI is centered around REF (1.50V). ITEC is zero when VCTLI = 1.50V. When VCTLI > 1.50V, the MAX1978 is heating. Current flow is from OS2 to OS1. The voltages are: VOS2 > VOS1 > VCS REF Figure 4. Proportional Integral Derivative Controller 16 when VCTLI < 1.50V, current flows from OS1 to OS2: VOS2 < VOS1 < VCS ______________________________________________________________________________________ Integrated Temperature Controllers for Peltier Modules ITEC Output ITEC is a status output that provides a voltage proportional to the actual TEC current. ITEC = REF when TEC current is zero. The transfer function for the ITEC output: VITEC = 1.50 + 8 ✕ (VOS1 - VCS) Use ITEC to monitor the cooling or heating current through the TEC. The maximum capacitance that ITEC can drive is 100pF. Applications Information The MAX1978/MAX1979 drive a thermoelectric cooler inside a thermal-control loop. TEC drive polarity and power are regulated to maintain a stable control temperature based on temperature information read from a thermistor, or from other temperature-measuring devices. Carefully selected external components can achieve 0.001°C temperature stability. The MAX1978/ MAX1979 provide precision amplifiers and an integrator amplifier to implement the thermal-control loop (Figures 1 and 2). Connecting and Compensating the Thermal-Control Loop Typically, the thermal loop consists of an error amplifier and proportional integral derivative controller (PID) (Figure 4). The thermal response of the TEC module must be understood before compensating the thermal loop. In particular, TECs generally have stronger heating capacity than cooling capacity because of the effects of waste heat. Consider this point when analyzing the TEC response. Analysis of the TEC using a signal analyzer can ease compensation calculations. Most TECs can be crudely modeled as a two-pole system. The second pole potentially creates an oscillatory condition because of the associated 180° phase shift. A dominant pole compensation scheme is not practical because the crossover frequency (the point of the Bode plot where the gain is zero dB) must be below the TEC’s first pole, often as low as 0.02Hz. This requires an excessively large inte- grator capacitor and results in slow loop-transient response. A better approach is to use a PID controller, where two additional zeros are used to cancel the TEC and integrator poles. Adequate phase margin can be achieved near the frequency of the TEC’s second pole when using a PID controller. The following is an example of the compensation procedure using a PID controller. Figure 6 details a two-pole transfer function of a typical TEC module. This Bode plot can be generated with a signal analyzer driving the CTLI input of the MAX1978/MAX1979, while plotting the thermistor voltage from the module. For the example module, the two poles are at 0.02Hz and 1Hz. The first step in compensating the control loop involves selecting components R3 and C2 for highest DC gain. Film capacitors provide the lowest leakage but can be large. Ceramic capacitors are a good compromise between low leakage and small size. Tantalum and electrolytic capacitors have the highest leakage and generally are not suitable for this application. The integrating capacitor, C2, and R3 (Figure 4) set the first zero (fz1). The specific application dictates where the first zero should be set. Choosing a very low frequency results in a very large value capacitor. Set the first zero frequency to no more than 8 times the frequency of the lowest TEC pole. Setting the frequency more than 8 times the lowest pole results in the phase falling below -135° and may cause instability in the system. For this example, C2 = 10µF. Resistor R3 then sets the zero at 0.16Hz using the following equation: fz1 = 1 2π × C2 × R3 This yields a value of R3 = 99.47kΩ. For our example, use 100kΩ. Next, adjust the gain for a crossover frequency for maximum phase margin near the TEC’s second pole. From Figure 6, the TEC bode plot, approximately 30dB of gain is needed to move the 0dB crossover point up to 1.5Hz. The error amplifier provides a fixed gain of 50, or approximately 34dB. Therefore, the integrator needs to provide -4dB of gain at 1.5Hz. C1 and R3 set the gain at the crossover frequency. C1 = A 1 + 2π × R3 × fC C2 ______________________________________________________________________________________ 17 MAX1978/MAX1979 Shutdown Control Drive SHDN low to place the MAX1978/MAX1979 in a power-saving shutdown mode. When the MAX1978/ MAX1979 are in shutdown, the TEC is off (VOS1 and VOS2 decay to GND) and input supply current lowers to 2mA (typ). where: A = The gain needed to move the 0dB crossover point up to the desired frequency. In this case, A = -4dB = 0.6. fC = The desired crossover frequency, 1.5Hz in this example. C1 is found to be 0.58µF; use 0.47µF. Next, the second TEC pole must be cancelled by adding a zero. Canceling the second TEC pole provides maximum phase margin by adding positive phase to the circuit. Setting a second zero (fz2) to at least 1/5 the crossover frequency (1.5Hz/5 = 0.3Hz), and a pole (fp1) to 5 times the crossover frequency or higher (5 × 1.5Hz = 7.5Hz) ensures good phase margin, while allowing for variation in the location of the TEC’s second pole. Set the zero fz2 to 0.3Hz and calculate R2: 1 fz2 = 2π × C1× R2 where fz2 is the second zero. R2 is calculated to be 1.1MΩ; use 1MΩ. Now pole fp1 is added at least 5 times the crossover frequency to terminate zero fz2. Choose fp1 = 15Hz, find R1 using the following equation: Resistor R1 is found to be 22kΩ, use 20kΩ The final step is to terminate the first zero by setting the rolloff frequency with a second pole, fp2. A good choice is 2 times fp1. Choose fp2 = 30Hz, find C3 using the following equation: fp2 = where C3 is found to be 0.05µF, use 0.047µF. Figure 7 displays the compensated gain and phase plots for the above example. The example given is a good place to start when compensating the thermal loop. Different TEC modules require individual testing to find their optimal compensation scheme. Other compensation schemes can be used. The above procedure should provide good results for the majority of optical modules. Chip Information TRANSISTOR COUNT: 6023 PROCESS: BiCMOS 1 2π × C1× R1 COMPENSATED TEC GAIN AND PHASE TEC GAIN AND PHASE 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 -80 0.001 90 -45 -90 -135 0.1 1 10 FREQUENCY (Hz) Figure 6. Bode Plot of a Generic TEC Module 18 -180 100 GAIN (dB) 0 PHASE (DEGREES) 45 0.01 1 2π × C3 × R3 80 70 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 -80 0.001 90 45 0 -45 -90 PHASE (DEGREES) fp1 = GAIN (dB) MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules -135 0.01 0.1 1 10 -180 100 FREQUENCY (Hz) Figure 7. Compensated Thermal-Control Loop Using the TEC Module in Figure 6 ______________________________________________________________________________________ Integrated Temperature Controllers for Peltier Modules INPUT 3V TO 5.5V VDD PVDD- LX1 PGND1 ON CS SHDN OFF OVERTEMP ALARM OT UNDERTEMP ALARM UT BFB- OS1 MAX1978 TEC OS2 ITEC = ±3A LX2 PGND2 AIN- TEMP MONITOR REF AOUT FB+ TEC CURRENT MONITOR ITEC AIN+ NTC VOLTAGE LIMIT MAXV HEATING CURRENT LIMIT MAXIP COOLING CURRENT LIMIT MAXIN FBOPTIONAL DAC DAC REF ______________________________________________________________________________________ 19 MAX1978/MAX1979 Typical Operating Circuit Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 32, 44, 48L QFN .EPS MAX1978/MAX1979 Integrated Temperature Controllers for Peltier Modules D2 D CL D/2 b D2/2 k E/2 E2/2 E CL (NE-1) X e E2 k L DETAIL A e (ND-1) X e CL CL L L e A1 A2 e A PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE 32, 44, 48L QFN THIN, 7x7x0.8 mm APPROVAL DOCUMENT CONTROL NO. 21-0144 COMMON DIMENSIONS REV. 1 A 2 EXPOSED PAD VARIATIONS ** NOTE: T4877-1 IS A CUSTOM 48L PKG. WITH 4 LEADS DEPOPULATED. TOTAL NUMBER OF LEADS ARE 44. PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE 32, 44, 48L QFN THIN, 7x7x0.8 mm APPROVAL DOCUMENT CONTROL NO. 21-0144 REV. A 2 2 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. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.