Electronic Components Datasheet Search |
|
MAX1968 Datasheet(PDF) 11 Page - Maxim Integrated Products |
|
MAX1968 Datasheet(HTML) 11 Page - Maxim Integrated Products |
11 / 16 page Power Drivers for Peltier TEC Modules ______________________________________________________________________________________ 11 Detailed Description The MAX1968/MAX1969 TEC drivers consist of two switching buck regulators that operate together to directly control TEC current. This configuration creates a differential voltage across the TEC, allowing bidirec- tional TEC current for controlled cooling and heating. Controlled cooling and heating allow accurate TEC temperature control within the tight tolerances of laser driver specifications. The voltage at CTLI directly sets the TEC current. An external thermal-control loop is typ- ically used to drive CTLI. Figures 1 and 2 show exam- ples of thermal control-loop circuits. Ripple Cancellation Switching regulators like those used in the MAX1968/MAX1969 inherently create ripple voltage on the output. The regulators in the MAX1968 switch in phase and provide complementary in-phase duty cycles so ripple waveforms at the TEC are greatly reduced. This feature suppresses ripple currents and electrical noise at the TEC to prevent interference with the laser diode. Switching Frequency FREQ sets the switching frequency of the internal oscil- lator. With FREQ = GND, the oscillator frequency is set to 500kHz. The oscillator frequency is 1MHz when FREQ = VDD. Voltage and Current-Limit Settings Both the MAX1968 and MAX1969 provide control of the maximum differential TEC voltage. Applying a voltage to MAXV limits the maximum voltage across the TEC. The MAX1968 provides control of the maximum positive and negative TEC current. The voltage at MAXIP and MAXIN sets the maximum positive and negative current through the TEC. These current limits can be indepen- dently controlled. The MAX1969 only controls TEC cur- rent in one direction. The maximum TEC current is controlled by MAXIP. Connect MAXIN to GND when using the MAX1969. Current Monitor Output ITEC provides a voltage output proportional to the TEC current (ITEC). See the Functional Diagram for more detail: VITEC = 1.5V + 8 x (VOS1 - VCS) Reference Output The MAX1968/MAX1969 include an on-chip voltage ref- erence. The 1.50V reference is accurate to 1% over temperature. Bypass REF with 1µF to GND. REF may be used to bias an external thermistor for temperature sensing as shown in Figures 1 and 2. Design Procedure Inductor Selection Small surface-mount inductors are ideal for use with the MAX1968/MAX1969. 3.3µH inductors are suitable for most applications. Select the output inductors so that the LC resonant frequency of the inductance and the output capacitance is less than 1/5 the selected switch- ing frequency. For example, 3.3µH and 1µF have a res- onance at 87.6kHz, which is adequate for 500kHz operation where: f = resonant frequency of output filter. Capacitor Selection Filter Capacitors Decouple each power-supply input (VDD, PVDD1, PVDD2) with a 1µF ceramic capacitor close to the supply pins. In some applications with long distances between the source supply and the MAX1968/MAX1969, addition- al bypassing may be needed to stabilize the input sup- ply. In such cases, a low-ESR electrolytic capacitor of 100µF or more at VDD is usually sufficient. Compensation Capacitor A compensation capacitor is needed to ensure current control-loop stability. Select the capacitor so that the unity-gain bandwidth of the current control loop is less than or equal to 1/12th the resonant frequency of the out- put filter: where: fBW = loop unity gain bandwidth gm = loop transconductance, typically 100µA/V CCOMP = value of the compensation capacitor RTEC = TEC series resistance RSENSE = sense resistor C g f R RR For MAX C g f R RR For MAX COMP m BW SENSE SENSE TEC COMP m BW SENSE SENSE TEC ≥ ⎛ ⎝⎜ ⎞ ⎠⎟ × × ×+ ⎛ ⎝⎜ ⎞ ⎠⎟ ≥ ⎛ ⎝⎜ ⎞ ⎠⎟ × × ×+ ⎛ ⎝⎜ ⎞ ⎠⎟ 24 2 1968 12 2 1969 π π () () () () f LC = 1 2 π |
Similar Part No. - MAX1968_07 |
|
Similar Description - MAX1968_07 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |