Integrated Temperature Controllers Peltier Modules Smallest, Safe

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Integrated Temperature Controllers Peltier Modules Smallest, Safe

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19-2490; 7/02
Integrated Temperature Controllers Peltier Modules
Smallest, Safest, Most Accurate Complete Single-Chip Controller On-Chip Power MOSFETS-No External FETs Circuit Footprint 0.93in2 Circuit Height Temperature Stability 0.001°C Integrated Precision Integrator Chopper Stabilized Amps Accurate, Independent Heating Cooling Current Limits Eliminates Surges Directly Controlling Current Adjustable Differential Voltage Limit Low-Ripple Low-Noise Design Current Monitor Temperature Monitor Over- Undertemperature Alarm Bipolar Output Current (MAX1978)
MAX1978/MAX1979
MAX1978/MAX1979 smallest, safest, most accurate complete single-chip temperature controllers Peltier thermoelectric cooler (TEC) modules. On-chip power FETs thermal control-loop circuitry minimize external components while maintaining high efficiency. Selectable 500kHz/1MHz switching frequency unique ripple-cancellation scheme optimize component size efficiency while reducing noise. Switching speeds internal MOSFETs optimized reduce noise EMI. ultralow-drift chopper amplifier maintains ±0.001°C temperature stability. Output current, rather than voltage, directly controlled eliminate current surges. Individual heating cooling current voltage limits provide highest level protection. MAX1978 operates from single supply provides bipolar output biasing between outputs synchronous buck regulators. True bipolar operation controls temperature without "dead zones" other nonlinearities load currents. control system does hunt when point very close natural operating point, where only small amount heating cooling needed. analog control signal precisely sets current. MAX1979 provides unipolar output chopper-stabilized instrumentation amplifier highprecision integrator amplifier supplied create proportional-integral (PI) (PID) controller. instrumentation amplifier interface external thermistor, thermocouple, semiconductor temperature sensor. Analog outputs provided monitor temperature current. addition, separate overtemperature undertemperature outputs indicate when temperature range. on-chip voltage reference provides bias thermistor bridge. MAX1978/MAX1979 available low-profile 48-lead thin QFN-EP package specified over -40°C +85°C temperature range. thermally enhanced QFN-EP package with exposed metal minimizes operating junction temperature. evaluation available speed designs.
Unipolar Output Current (MAX1979)
Ordering Information
PART MAX1978EMAX1979E*EP Exposed pad. TEMP RANGE -40°C +85°C -40°C +85°C PIN-PACKAGE Thin QFN-EP* Thin QFN-EP
Configuration
MAXV MAXIN CTLI
ITEC
VIEW
MAXIP COMP
N.C. PGND2 PGND2 PVDD2 N.C. PVDD2 SHDN
FREQ N.C. PGND1 PGND1 PVDD1 N.C. PVDD1
Applications
Fiber Optic Laser Modules WDM, DWDM Laser-Diode Temperature Control Fiber Optic Network Equipment EDFA Optical Amplifiers Telecom Fiber Interfaces
Typical Operating Circuit appears data sheet.
MAX1978 MAX1979
INTGND DIFOUT FBFB+
BFBBFB+
INTOUT
QFN-EP
*ELECTRICALLY CONNECTED UNDERSIDE METAL SLUG. NOTE: CONNECTED UNDERSIDE METAL SLUG.
Maxim Integrated Products
AIN+ AINAOUT
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
ABSOLUTE MAXIMUM RATINGS
.-0.3V SHDN, MAXV, MAXIP, MAXIN, CTLI, GND.-0.3V FREQ, COMP, OS1, OS2, REF, ITEC, AIN+, AIN-, AOUT, INT-, INTOUT, BFB+, BFB-, FB+, FB-, DIFOUT GND.-0.3V (VDD 0.3V) PVDD1, PVDD2 .-0.3V +0.3V PVDD1, PVDD2 GND.-0.3V (VDD 0.3V) PGND1, PGND2 .-0.3V +0.3V COMP, REF, ITEC, INTOUT, DIFOUT, BFB-, BFB+, AOUT Short .Indefinite Peak Current (MAX1978) (Note 1).±4.5A Peak Current (MAX1979) (Note 1).+9A Continuous Power Dissipation +70°C) 48-Lead Thin QFN-EP (derate 26.3mW/°C above +70°C) (Note .2.105W Operating Temperature Ranges MAX1978E.-40°C +85°C MAX1979E.-40°C +85°C Maximum Junction Temperature .+150°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Note internal clamp diodes PGND PVDD. Applications that forward bias these diodes should exceed IC's package power dissipation limits. Note Solder underside metal slug board ground plane.
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD PVDD1 PVDD2 SHDN FREQ GND, CTLI MAXV MAXIP MAXIN REF, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER Input Supply Range SYMBOL ITEC ±3A, VOUT VOS1 VOS2 (MAX1978) ITEC VOUT VOS1 (MAX1979) ITEC ±3A, VOUT VOS1 VOS2 (MAX1978) ITEC VOUT VOS1 (MAX1979) Maximum Current Reference Voltage Reference Load Regulation ITEC(MAX) VREF VREF MAX1978 MAX1979 5.5V, IREF 150µA 5.5V, IREF +10µA -1mA VOS1 Current-Sense Threshold VOS1 NFET On-Resistance PFET On-Resistance NFET Leakage RDS(ON-N) RDS(ON-P) ILEAK(N) 0.5A 0.5A 0.5A 0.5A +25°C +85°C VMAXI_ VREF VMAXI_ VREF/3 VMAXI_ VREF VMAXI_ VREF/3 1.485 1.500 0.04 0.06 0.06 0.09 0.02 -2.3 CONDITIONS -4.3 +4.3 +2.3 1.515 0.07 0.08 0.10 0.12 UNITS
Output Voltage Range
VOUT
Integrated Temperature Controllers Peltier Modules
ELECTRICAL CHARACTERISTICS (continued)
(VDD PVDD1 PVDD2 SHDN FREQ GND, CTLI MAXV MAXIP MAXIN REF, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER PFET Leakage No-Load Supply Current Shutdown Supply Current Thermal Shutdown UVLO Threshold Switching Frequency Internal Oscillator OS1, OS2, Input Current SHDN, FREQ Input Current SHDN, FREQ Input Voltage SHDN, FREQ Input High Voltage SYMBOL ILEAK(P) IDD(NO
LOAD)
MAX1978/MAX1979
CONDITIONS +25°C +85°C 3.3V SHDN GND, (Note rising falling FREQ FREQ=VDD 5.5V 5.5V VMAXV VREF 0.67, VOS1 VOS2 ±4V, VMAXV VREF 0.33, VOS1 VOS2 ±2V,
0.02
2.75 1200 +100 0.25
UNITS
IDD-SD
TSHUTDOWN Hysteresis 15°C VUVLO fSW-INT IOS1, IOS2, ISHDN, IFREQ 2.25 -100
1000
0.75 -0.1 -0.1
MAXV Threshold Accuracy
+0.1 10.5 +0.1 +200 µV/°C
MAXV, MAXIP, MAXIN Input Bias Current CTLI Gain CTLI Input Resistance Error Transconductance ITEC Accuracy ITEC Load Regulation Instrumentation Input Bias Current Instrumentation Offset Voltage Instrumentation OffsetVoltage Drift with Temperature Instrumentation Preset Gain
IMAXV-BIAS, VMAXV VMAXI_ 0.1V 1.5V IMAXI_-BIAS ACTLI RCTLI VOS1 +100mV -100mV VITEC IDIF-BIAS VDIF-OS 5.5V 5.5V ADIF RLOAD VOS1 +100mV -100mV, IITEC ±10µA VCTLI 0.5V 2.5V (Note terminated
-200
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
ELECTRICAL CHARACTERISTICS (continued)
(VDD PVDD1 PVDD2 SHDN FREQ GND, CTLI MAXV MAXIP MAXIN REF, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER Integrator Open-Loop Gain Integrator CMRR Integrator Input Bias Current Integrator Voltage Offset Integrator Gain Bandwidth Undedicated Chopper Open-Loop Gain Undedicated Chopper CMRR Undedicated Chopper Input Bias Current Undedicated Chopper Offset Voltage Undedicated Chopper Gain Bandwidth Undedicated Chopper Output Ripple BFB_ Buffer Error Leakage Current Output Voltage Trip Threshold Trip Threshold ILEAK SYMBOL AOL-INT CMRRINT IINT-BIAS VINT-OS GBWINT AOL-AIN CMRRAIN IAIN-BIAS VAIN-OS GBWAIN VRIPPLE CLOAD 100pF 5.5V Sinking (see Typical Application Circuit) (see Typical Application Circuit) -200 5.5V 5.5V -200 RLOAD 5.5V 5.5V +0.1 +200 +200 CONDITIONS RLOAD UNITS
Integrated Temperature Controllers Peltier Modules
ELECTRICAL CHARACTERISTICS
(VDD PVDD1 PVDD2 SHDN FREQ GND, CTLI MAXV MAXIP MAXIN REF, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER Input Supply Range SYMBOL ITEC ±3A, VOUT VOS1 -VOS2 (MAX1978) ITEC VOUT VOS1 (MAX1979) ITEC ±3A, VOUT VOS1 VOS2 (MAX1978) ITEC VOUT VOS1 (MAX1979) Maximum Current Reference Voltage Reference Load Regulation ITEC(MAX) VREF VREF MAX1978 MAX1979 5.5V, IREF 150µA 5.5V, IREF 10µA -1mA VOS1 Current-Sense Threshold VOS1 No-Load Supply Current Shutdown Supply Current UVLO Threshold Switching Frequency Internal Oscillator OS1, OS2, Input Current SHDN, FREQ Input Current SHDN, FREQ Input Voltage SHDN, FREQ Input High Voltage IDD(NO
LOAD)
MAX1978/MAX1979
CONDITIONS
-4.3
+4.3
UNITS
Output Voltage Range
VOUT
-2.3 +2.3 1.475 1.515
VMAXI_ VREF VMAXI_ VREF/3 VMAXI_ VREF VMAXI_ VREF/3
3.3V SHDN GND, (Note rising falling FREQ FREQ 2.25 -100
IDD-SD VUVLO fSW-INT
2.75 1200 +100 0.25
IOS1, IOS2, SHDN, FREQ 5.5V 5.5V
0.75
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
ELECTRICAL CHARACTERISTICS (continued)
(VDD PVDD1 PVDD2 SHDN FREQ GND, CTLI MAXV MAXIP MAXIN REF, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER SYMBOL CONDITIONS VMAXV VREF 0.67, VOS1 VOS2 ±4V, VMAXV VREF 0.33, VOS1 VOS2 ±2V, MAXV, MAXIP, MAXIN Input Bias Current CTLI Gain CTLI Input Resistance Error Transconductance ITEC Accuracy ITEC Load Regulation Instrumentation Input Bias Current Instrumentation Offset Voltage Instrumentation Preset Gain Integrator Input Bias Current Integrator Voltage Offset Undedicated Chopper Input Bias Current Undedicated Chopper Offset Voltage BFB_ Buffer Error Leakage Current Output Voltage ILEAK VITEC IDIF-BIAS VDIF-OS ADIF IINT-BIAS VINT-OS IAIN-BIAS VAIN-OS 5.5V RLOAD 5.5V 5.5V 5.5V 5.5V CLOAD 100pF 5.5V Sinking -200 -200 IMAXV-BIAS, VMAXV VMAXI_ 0.1V 1.5V IMAXI_-BIAS ACTLI RCTLI VOS1 +100mV -100mV VOS1 +100mV -100mV, IITEC ±10µA VCTLI 0.5V 2.5V (Note terminated -0.1 -0.125 -200 +0.1 10.5 +0.125 +200 +200 +200 UNITS
MAXV Threshold Accuracy
Note Includes power leakage. Note CTLI gain defined
CTLI (VCTLI -VREF
(VOSI -VCS
Note Specifications -40°C guaranteed design, production tested.
Integrated Temperature Controllers Peltier Modules
Typical Operating Characteristics
(VDD VCTLI VFREQ GND, RTEC circuit Figure +25°C, unless otherwise noted.)
EFFICIENCY CURRENT
MAX1978 toc01
MAX1978/MAX1979
EFFICIENCY CURRENT 3.3V
MAX1978 toc02
OUTPUT-VOLTAGE RIPPLE WAVEFORMS
VOS2 100mV/div AC-COUPLED
MAX1978 toc03
EFFICIENCY RTEC
EFFICIENCY RTEC 0.855
VOS1 100mV/div AC-COUPLED
VOS1 VOS1 50mV/div
400ns/div
CURRENT
CURRENT
INPUT SUPPLY RIPPLE
MAX1978 toc04
CURRENT CTLI VOLTAGE
MAX1978 toc05
ZERO-CROSSING CURRENT
VCTLI 200mV/div
MAX1978 toc06
1.5V 20mV/div AC-COUPLED VCTLI 1V/div ITEC 2A/div ITEC 500mA/div
200ns/div
20ms/div
1ms/div
VITEC CURRENT
MAX1978 toc07
CURRENT TEMPERATURE
MAX1978 toc08
SWITCHING FREQUENCY TEMPERATURE
SWITCHING FREQUENCY (kHz) VCTLI 1.5V RTEC
MAX1978 toc09
VITEC
1.010
1.005 ITEC
1.000
0.995 CURRENT 0.990 TEMPERATURE (°C) ITEC RSENSE 0.68
TEMPERATURE (°C)
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
Typical Operating Characteristics (continued)
(VDD VCTLI VFREQ GND, RTEC circuit Figure +25°C, unless otherwise noted.)
SWITCHING FREQUENCY CHANGE INPUT SUPPLY
SWITCHING FREQUENCY CHANGE (kHz) REFERENCE VOLTAGE CHANGE (mV)
MAX1978 toc10
REFERENCE VOLTAGE CHANGE INPUT SUPPLY
MAX1978 toc11
REFERENCE VOLTAGE CHANGE TEMPERATURE
REFERENCE VOLTAGE CHANGE (mV)
MAX1978 toc12
-0.5 -1.0 -1.5 -2.0 -2.5 -3.0
TEMPERATURE (°C)
REFERENCE LOAD REGULATION
MAX1978 toc13
VOLTAGE THERMISTOR TEMPERATURE
MAX1978 toc14
STARTUP SHUTDOWN WAVEFORMS
VSHDN 5V/div
MAX1978 toc15
REFERENCE VOLTAGE CHANGE (mV)
VOLTAGE NTC, THERMISTOR CIRCUIT FIGURES
-0.2 -0.4 -0.6 -0.8 -1.0 -0.4 -0.2 REFERENCE LOAD CURRENT (mA) SINK SOURCE
ITEC 500mA/div
200mA/div 100µs/div
THERMISTOR TEMPERATURE (°C)
CTLI STEP RESPONSE
MAX1978 toc16
INPUT SUPPLY STEP RESPONSE
2V/div
MAX1978 toc17
THERMAL STABILITY, COOLING MODE
MAX1978 toc18
VCTLI 1V/div
1.5V TEMPERATURE 0.001°C/div
ITEC 1A/div
ITEC 20mA/div
ITEC +25°C +45°C
1ms/div
10ms/div
4s/div
Integrated Temperature Controllers Peltier Modules
Typical Operating Characteristics (continued)
(VDD VCTLI VFREQ GND, RTEC circuit Figure +25°C, unless otherwise noted.)
THERMAL STABILITY, ROOM TEMPERATURE
MAX1978 toc19
MAX1978/MAX1979
THERMAL STABILITY, HEATING MODE
MAX1978 toc20
TEMPERATURE ERROR AMBIENT TEMPERATURE
MAX1978 toc21
0.03 0.02 TEMPERATURE ERROR (°C) 0.01 -0.01 -0.02 -0.03
TEMPERATURE 0.001°C/div
TEMPERATURE 0.001°C/div
ITEC +25°C +25°C
TTEC +25°C +5°C
4s/div
4s/div
AMBIENT TEMPERATURE (°C)
Description
NAME N.C. PGND2 PVDD2 SHDN FUNCTION Output Sense senses side differential voltage. sense point, power output. Internally Connected Power Ground Internal synchronous rectifier ground connections. Connect PGND pins together power ground plane. Inductor Connection. Connect pins together. Connect when using MAX1979. Power Inputs. Must same voltage VDD. Connect PVDD2 inputs together power plane. Bypass PGND2 with 10µF ceramic capacitor. Shutdown Control Input. Active-low shutdown control. Under-Temperature Alarm. Open-drain output pulls temperature feedback falls 20mV (typically +1.5°C) below set-point voltage. Under-Temperature Alarm. Open-drain output pulls temperature feedback falls 20mV (typically +1.5°C) below set-point voltage. Integrator Inverting Input. Normally connected DIFOUT through thermal-compensation network. Analog Ground. Connect pins analog ground plane.
INTOUT Integrator Output. Normally connected CTLI. INTGND
DIFOUT Chopper-Stabilized Instrumentation Output. Differential gain (FB+ FB-). FBFB+ BFBBFB+ AIN+ Chopper-Stabilized Instrumentation Inverting Input. Connect thermistor bridge. Chopper-Stabilized Instrumentation Noninverting Input. Connect thermistor bridge. Chopper-Stabilized Buffered Output. Used monitor thermistor bridge voltage. Chopper-Stabilized Buffered Output. Used monitor thermistor bridge voltage. Undedicated Chopper-Stabilized Amplifier Noninverting Input
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
Description (continued)
NAME AINAOUT PVDD1 PGND1 FREQ ITEC COMP MAXIP MAXIN MAXV CTLI FUNCTION Undedicated Chopper-Stabilized Amplifier Inverting Input Undedicated Chopper-Stabilized Amplifier Output Power Inputs. Must same voltage VDD. Connect PVDD1 inputs together power plane. Bypass PGND1 with 10µF ceramic capacitor. Inductor Connection. Connect pins together. Connect when using MAX1979. Power Ground Internal synchronous-rectifier ground connections. Connect PGND pins together power ground plane. Switching-Frequency Select. 500kHz, high 1MHz. Current Monitor Output. ITEC output voltage function voltage across currentsense resistor. VITEC 1.50V (VOS1 VCS) Current-Control Loop Compensation. most designs, connect 10nF capacitor from COMP GND. Maximum Positive Current. Connect MAXIP default positive current limit +150mV RSENSE. Maximum Negative Current. Connect MAXIN default negative current limit -150mV RSENSE. Connect MAXIN when using MAX1979. Maximum Bipolar Voltage. Connect external resistive divider from maximum voltage across TEC. maximum voltage VMAXV. Analog Supply Voltage Input. Bypass with 10µF ceramic capacitor. Current-Control Input. Sets differential current into TEC. Center point 1.50V current). Connect INTOUT when using thermal control loop. ITEC (VOS1 VCS) RSENSE (VCTLI 1.50) RSENSE). When (VCLTI VREF) VOS2 VOS1 VCS. 1.5V Reference Voltage Output. Bypass with ceramic capacitor. Current-Sense Input. current through monitored between OS1. maximum current given 150mV RSENSE bipolar MAX1978. MAX1979 current unipolar. Output Sense senses side differential voltage. sense point, power output.
Integrated Temperature Controllers Peltier Modules
Functional Diagram
SHDN 1.5V REFERENCE FREQ PVDD1 5.5V
MAX1978/MAX1979
MAXV
VTEC VMAXV
MAXIP
ITEC (VMAXIP/ VREF) (0.15V/RSENSE) PGND1 ITEC (VMAXIN/ VREF) (0.15V/RSENSE) CONTROL GATE DRIVE
MAXIN
RSENSE
ITEC
CTLI COMP
PVDD2
MAX1978
PGND2
BFB-
BFB+ INTOUT INTAINAOUT AIN+ DIFOUT
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
Detailed Description
Power Stage
power stage MAX1978/MAX1979 thermoelectric cooler (TEC) temperature controllers consists switching buck regulators that operate together directly control current. This configuration creates differential voltage across TEC, allowing bidirectional current controlled cooling heating. Controlled cooling heating allow accurate temperature control within tight tolerances laser driver specifications. voltage CTLI directly sets current. internal thermal-control loop drives CTLI regulate temperature. on-chip thermal-control circuitry configured achieve temperature control stability 0.001°C. Figure shows typical thermalcontrol circuit.
Ripple Cancellation
Switching regulators like those used MAX1978/MAX1979 inherently create ripple voltage each common-mode output. regulators MAX1978 switch phase provide complementary in-phase duty cycles, ripple waveforms differential output greatly reduced. This feature suppresses ripple currents electrical noise prevent interference with laser diode while minimizing output capacitor filter size.
10µF 10µF
10µF
0.01µF
COMP
SHDN
PVDD1
PVDD2
MAXV MAXIN MAXIP
0.068
UNDERTEMP ALARM OVERTEMP ALARM CURRENT MONITOR
ITEC
MAX1978
BFBAINAOUT AIN+
4.7µF
80.6k THERMISTOR VOLTAGE MONITOR 69.8k
PGND2 PGND1 INTOUT INTFBDIFOUT 100k 100k 10µF 0.47µF THERMAL FEEDBACK
105k
CTLI FREQ
0.047µF
Figure MAX1978 Typical Application Circuit
Integrated Temperature Controllers Peltier Modules
Switching Frequency
FREQ sets switching frequency internal oscillator. oscillator frequency 500kHz when FREQ GND. oscillator frequency 1MHz when FREQ VDD. 1MHz setting allows minimum inductor filter-capacitor values. Efficiency optimized with 500kHz setting. derived from, synchronized switching frequency power stage.
MAX1978/MAX1979
Integrator Amplifier
on-chip integrator amplifier provided MAX1978/MAX1979. noninverting terminal amplifier connected internally REF. Connect appropriate network resistors capacitors between DIFOUT INT-, connect INTOUT CTLI typical operation. CTLI directly controls current magnitude polarity. thermal-control-loop dynamics integrator input feedback components. Applications Information section details thermal-loop compensation.
Voltage Current-Limit Settings
MAX1978 MAX1979 provide settings limit maximum differential voltage. Applying voltage MAXV limits maximum voltage across VMAXV). MAX1978 also limits maximum positive negative current. voltages applied MAXIP MAXIN independently maximum positive negative output current limits. MAX1979 controls current only direction, maximum current only with MAXIP. MAXIN must connected when using MAX1979.
Current Monitor Output
ITEC provides voltage output proportional current, ITEC (see Functional Diagram): VITEC 1.5V (VOS1 VCS)
Chopper-Stabilized Instrumentation Amplifier
MAX1978 MAX1979 include chopped input instrumentation amplifier with fixed gain external thermal sensor, typically thermistor, connected amp's inputs. other input connected voltage that represents temperature point. This point derived from resistordivider network DAC. included instrumentation amplifier provides offset drift needed prevent temperature set-point drift with ambient temperature changes. Temperature stability 0.001°C achieved over +50°C ambient temperarure range using amplifier Figure DIFOUT instrumentation amplifier output proportional times difference between set-point temperature temperature. This difference commonly referred "error signal". best temperature stability, derive set-point voltage from same reference that drives thermistor (usually MAX1978/MAX1979 output). This called "ratiometric" "bridge" connection. bridge connection optimizes stability eliminating drift error source. Errors nullified because they affect thermistor point equally. instrumentation amplifier utilizes chopped input scheme minimize input offset voltage drift. This generates output ripple DIFOUT that equal chop frequency. DIFOUT peak-to-peak ripple amplitude typically 100mV effect temperature stability. DIFOUT ripple filtered integrator following stage. chopper frequency
Over- Under-Temperature Alarms
MAX1978/MAX1979 provide open-drain status outputs that alert microcontroller when temperature over under set-point temperature. pull when V(FB1+ FB-) more than 20mV. typical thermistor connection, this translates approximately 1.5°C error.
Reference Output
MAX1978/MAX1979 include on-chip 1.5V voltage reference accurate over temperature. Bypass with GND. used bias external thermistor temperature sensing shown Figures Note that accuracy does limit temperature stability achievable with MAX1978/MAX1979. This because thermistor set-point bridge legs intended driven ratiometrically same reference source (REF). Variations bridge-drive voltage then cancel generate errors. Consequently, 0.001°C stable temperature control achievable with MAX1978/MAX1979 reference. external source used bias thermistor bridge. best accuracy, common-mode voltage applied should kept between 0.5V however input range extended from 0.2V some shift instrumentation offset (approximately -50µV/V) tolerated. This shift remains constant with temperature does contribute set-point drift.
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
10µF 10µF
10µF
0.01µF
COMP
SHDN
PVDD1
PVDD2
UNDERTEMP ALARM OVERTEMP ALARM CURRENT MONITOR
ITEC
MAXV MAXIN MAXIP
0.03
MAX1979
BFBAINAOUT
4.7µF
80.6k THERMISTOR VOLTAGE MONITOR 69.8k
AIN+ 105k CTLI FREQ PGND2 PGND1 INTOUT INTDIFOUT 100k FBFB+
THERMAL FEEDBACK
100k
10µF
0.47µF
0.047µF
Figure MAX1979 Typical Application Circuit
Buffered Outputs, BFB+ BFBBFB+ BFB- output buffered version voltage that appears FB-, respectively. buffers typically used conjunction with undedicated chopper amplifier create monitor thermistor voltage/TEC temperature (Figures These buffers unity-gain chopper amplifiers exhibit output ripple. Each output either integrated filtered remove ripple content necessary.
tional analog output. thermistor voltage typically connected undedicated chopper amplifier through included buffers BFB+ BFB-. Figure shows configure undedicated amplifier thermistor voltage monitor. output voltage AOUT precisely linear, because thermistor linear. AOUT also chopper stabilized exhibits output ripple either integrated filtered remove ripple content necessary.
Undedicated Chopper-Stabilized Amplifier
addition chopper amplifiers DIFOUT BFB_, MAX1978/MAX1979 include additional chopper amplifier AOUT. This amplifier uncommitted intended provide temperature-propor14
Integrated Temperature Controllers Peltier Modules
69.8k AIN+ AOUT 105k
22µF 100µF ceramic capacitor between power plane power ground. Insufficient supply bypassing result supply bounce degraded accuracy. Compensation Capacitor Include compensation capacitor ensure currentpower control-loop stability. Select capacitor that unity-gain bandwidth current-control loop less than equal resonant frequency output filter: RSENSE CCOMP (RSENSE RTEC where: unity-gain bandwidth frequency loop transconductance, typically 100µA/V CCOMP value compensation capacitor RTEC series resistance RSENSE sense resistor
MAX1978/MAX1979
80.6k AIN-
MAX1978 MAX1979
BFB10k
FBVSETPOINT
Setting Voltage Current Limits
Figure Thermistor Voltage Monitor
Design Procedure
Inductor Selection
Small surface-mount inductors ideal with MAX1978/MAX1979. Select output inductors that resonant frequency inductance output capacitance less than selected switching frequency. example, 3.0µH have resonance 92kHz, which adequate 500kHz operation.
Consider parameters guarantee robust design. These parameters include maximum positive current, maximum negative current, maximum voltage allowed across TEC. These limits should used MAXIP, MAXIN, MAXV voltages. Setting Positive Negative Current MAXIP MAXIN maximum positive negative currents, respectively. default current limit ±150mV RSENSE when MAXIP MAXIN connected REF. maximum limits other than defaults, connect resistor-divider from VMAXI_. resistors 100k range. VMAXI_ related ITEC following equations: VMAXIP (ITECP(MAX) RSENSE) VMAXIN (ITECN(MAX) RSENSE) where ITECP(MAX) maximum positive current ITECN(MAX) maximum negative current. Positive current occurs when less than OS1: ITEC RSENSE when ITEC ITEC RSENSE when ITEC
where: resonant frequency output filter.
Capacitor Selection
Filter Capacitors Decouple each power-supply input (VDD, PVDD1, PVDD2) with 10µF ceramic capacitor close supply pins. long supply lines separate source supply from MAX1978/MAX1979, source supply high output impedance, place additional
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
MAX1979 controls current only direction (unipolar). maximum unipolar current applying voltage MAXIP. Connect MAXIN when using MAX1979. equation setting MAXIP same MAX1978 MAX1979. exceed positive negative current-limit specifications TEC. Refer manufacturer's data sheet these limits. Setting Voltage Apply voltage MAXV control maximum differential voltage. MAXV vary from REF. voltage across four times VMAXV positive negative.
FBFBREF CREF
MAX1978 MAX1979
VTHERMISTOR VSETPOINT
|VOS1 VOS2| VMAXV resistors from 100k form voltagedivider VMAXV. Thermal-Control Loop MAX1978/MAX1979 provide necessary amplifiers needed create thermal-control loop. Typically, chopper-stabilized instrumentation amplifier generates error signal integrator amplifier used create controller. Figure shows example simple implementation. error signal needed control loop generated from difference between point thermistor voltage. desired set-point voltage derived from potentiometer, DAC, other voltage source. Figure details required connections. Connect output controller CTLI. details, Applications Information section.
MAX1978 MAX1979
CREF VTHERMISTOR
VSETPOINT
DIGITAL INPUT
Figure Point Derived from Potentiometer
Control Inputs/Outputs
Current Control voltage CTLI directly sets current. CTLI typically driven from output temperature-control circuit CINTOUT. purposes following equations, assumed that positive current heating. transfer function relating current through (ITEC) VCTLI given
ITEC (VCTLI VREF) RSENSE)
INT-
DIFOUT
INTOUT
where VREF 1.50V ITEC (VOS1 VCS) RSENSE VCTLI centered around (1.50V). ITEC zero when VCTLI 1.50V. When VCTLI 1.50V, MAX1978 heating. Current flow from OS1. voltages are: VOS2 VOS1
Figure Proportional Integral Derivative Controller
when VCTLI 1.50V, current flows from OS2: VOS2 VOS1
Integrated Temperature Controllers Peltier Modules
Shutdown Control Drive SHDN place MAX1978/MAX1979 power-saving shutdown mode. When MAX1978/ MAX1979 shutdown, (VOS1 VOS2 decay GND) input supply current lowers (typ). ITEC Output ITEC status output that provides voltage proportional actual current. ITEC when current zero. transfer function ITEC output: VITEC 1.50 (VOS1 VCS) ITEC monitor cooling heating current through TEC. maximum capacitance that ITEC drive 100pF. grator capacitor results slow loop-transient response. better approach controller, where additional zeros used cancel integrator poles. Adequate phase margin achieved near frequency TEC's second pole when using controller. following example compensation procedure using controller. Figure details two-pole transfer function typical module. This Bode plot generated with signal analyzer driving CTLI input MAX1978/MAX1979, while plotting thermistor voltage from module. example module, poles 0.02Hz 1Hz. first step compensating control loop involves selecting components highest gain. Film capacitors provide lowest leakage large. Ceramic capacitors good compromise between leakage small size. Tantalum electrolytic capacitors have highest leakage generally suitable this application. integrating capacitor, (Figure first zero (fz1). specific application dictates where first zero should set. Choosing very frequency results very large value capacitor. first zero frequency more than times frequency lowest pole. Setting frequency more than times lowest pole results phase falling below -135° cause instability system. this example, 10µF. Resistor then sets zero 0.16Hz using following equation:
MAX1978/MAX1979
Applications Information
MAX1978/MAX1979 drive thermoelectric cooler inside thermal-control loop. drive polarity power regulated maintain stable control temperature based temperature information read from thermistor, from other temperature-measuring devices. Carefully selected external components achieve 0.001°C temperature stability. MAX1978/ MAX1979 provide precision amplifiers integrator amplifier implement thermal-control loop (Figures
Connecting Compensating Thermal-Control Loop
Typically, thermal loop consists error amplifier proportional integral derivative controller (PID) (Figure thermal response module must understood before compensating thermal loop. particular, TECs generally have stronger heating capacity than cooling capacity because effects waste heat. Consider this point when analyzing response. Analysis using signal analyzer ease compensation calculations. Most TECs crudely modeled two-pole system. second pole potentially creates oscillatory condition because associated 180° phase shift. dominant pole compensation scheme practical because crossover frequency (the point Bode plot where gain zero must below TEC's first pole, often 0.02Hz. This requires excessively large inte-
This yields value 99.47k. example, 100k. Next, adjust gain crossover frequency maximum phase margin near TEC's second pole. From Figure bode plot, approximately 30dB gain needed move crossover point 1.5Hz. error amplifier provides fixed gain approximately 34dB. Therefore, integrator needs provide -4dB gain 1.5Hz. gain crossover frequency.
Integrated Temperature Controllers Peltier Modules
where: gain needed move crossover point desired frequency. this case, -4dB 0.6. desired crossover frequency, 1.5Hz this example. found 0.58µF; 0.47µF. Next, second pole must cancelled adding zero. Canceling second pole provides maximum phase margin adding positive phase circuit. Setting second zero (fz2) least crossover frequency (1.5Hz/5 0.3Hz), pole (fp1) times crossover frequency higher 1.5Hz 7.5Hz) ensures good phase margin, while allowing variation location TEC's second pole. zero 0.3Hz calculate where second zero. calculated 1.1M; pole added least times crossover frequency terminate zero fz2. Choose 15Hz, find using following equation:
MAX1978/MAX1979
Resistor found 22k, final step terminate first zero setting rolloff frequency with second pole, fp2. good choice times fp1. Choose 30Hz, find using following equation:
where found 0.05µF, 0.047µF. Figure displays compensated gain phase plots above example. example given good place start when compensating thermal loop. Different modules require individual testing find their optimal compensation scheme. Other compensation schemes used. above procedure should provide good results majority optical modules.
Chip Information
TRANSISTOR COUNT: 6023 PROCESS: BiCMOS
GAIN PHASE
0.001 0.01 -135 -180 PHASE (DEGREES) 0.001
COMPENSATED GAIN PHASE
-135 -180 PHASE (DEGREES)
GAIN (dB)
GAIN (dB)
0.01
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure Bode Plot Generic Module
Figure Compensated Thermal-Control Loop Using Module Figure
Integrated Temperature Controllers Peltier Modules
Typical Operating Circuit
INPUT 5.5V PVDD-
MAX1978/MAX1979
PGND1
OVERTEMP ALARM UNDERTEMP ALARM SHDN BFB-
MAX1978
PGND2
ITEC
AIN-
TEMP MONITOR CURRENT MONITOR
AOUT ITEC AIN+ VOLTAGE LIMIT MAXV MAXIP MAXIN FBOPTIONAL
HEATING CURRENT LIMIT COOLING CURRENT LIMIT
Integrated Temperature Controllers Peltier Modules MAX1978/MAX1979
Package Information
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
.EPS
E2/2 (NE-1)
D2/2
DETAIL (ND-1)
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE THIN, 7x7x0.8
DOCUMENT CONTROL REV.
APPROVAL
21-0144
COMMON DIMENSIONS
EXPOSED VARIATIONS
NOTE: T4877-1 CUSTOM PKG. WITH LEADS DEPOPULATED. TOTAL NUMBER LEADS
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE THIN, 7x7x0.8
DOCUMENT CONTROL REV.
APPROVAL
21-0144
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2002 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

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