Compact DWDM laser Temperature

文章摘要：Figure 6. Long term Stability Plot (Maximum error 0.0018°C).Figure 6 shows a long-term (8 hour) stability plot. This plot shows that the maximum thermal error is 25µV or 1.8m°C. This test is done with a voltmeter taking readings every 10 seconds so the test bandwidth is somewhat limited. A key

Compact DWDM laser Temperature,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com

Figure 6. Long term Stability Plot (Maximum error 0.0018°C).

Figure 6 shows a long-term (8 hour) stability plot. This plot shows that the maximum thermal error is 25µV or 1.8m°C. This test is done with a voltmeter taking readings every 10 seconds so the test bandwidth is somewhat limited. A key reason for the excellent stability shown in this test is the MAX4238 Chopper Stabilized Op Amp. Chopper Stabilization holds offset and drift to a minimum. Furthermore, the op amp's shutdown pin is configured in parallel with the MAX8521's enable pin. This is done to limit the startup surge associated with the PID's integrating capacitor starting at the rail potential. Because the MAX4238 has a high output impedance in shut down mode, the CTLI pin of the MAX8521 charges the op amp output and integrating capacitor (C16) to 1.5 Volts, or zero current through the TEC module. The helps very much to limit the start up surge that would otherwise force the TEC module to take full current until the integrating capacitor discharges (20Sec).

Clearly the DWDM fiber optic system will replace single wavelength systems. Most vendors are starting with 100GHz spacing and have plans for 25GHz-channel spacing. Maxim Integrated Product's MAX8520/21 can easily provide the level of performance needed for 25GHz channel spacing making it an ideal foundation for designers working on DWDM fiber optic systems. Maxim is also able to provide the MAX8521 in an ultra small UCSP package, which is small enough to be integrated inside the laser module offering further space savings.


Figure 7.


Figure 8.

MAX8521 SINGLE OP AMP DESIGN

DESIGNATION	QTY	DESRIPTION
C8	1	0.047µF, 50V, X7R Ceramic Cap. (0402) Murata (GRM36X7R473K10)
C17	1	0.022µF, 50V, X7R, Ceramic Cap.(1206) Kemet (C1206C223K5RACTU)
C6, C7, C12-C14	5	0.1µF 16V X7R Ceramic Cap. (0402) Murata (GRM36X5R104K10)
C1-C3, C5, C11, C20	6	1µF 10V X5R Ceramic Cap. (0603) Taiyo Yuden (JMK107BJ105MG) Murata (GRM188R60J105KA)
C4	1	10µF 6.3V X5R Ceramic Cap. (0805) Taiyo Yuden (JMK212BJ106MG)
C9, C16, C18	3	10µF 6.3V X5R Ceramic Cap. (1206) Taiyo Yuden (JMK316BJ106ML)
C21	1	150µF Electrolytic Cap, Sanyo (10MV150SAX) (Note: 150µF Total Buss Capacitance or Stiff Line Input)
L1, L2	2	2.2µH, 1.6A Inductor Sumida (CDRH2D18-2R2)
Q1-Q3	3	NPN Bipolar Transistor, 40V SOT-23 Central Semi. (CMPT3904)
R1	1	0.1Ω, 1%, 0.25W, Sense Resistor (1206) Panasonic ERJ8RSFR10
R19	1	10Ω 5% resistor (0805)
R12-R15, R18	5	1kΩ 5% resistor (0402)
R9-R11	3	4.7kΩ 5% resistor (0402)
R20	1	10kΩ, 0.1%, 25ppm/C°, resistor (0805), Panasonic, (ERA6YEB103)
R3	1	49.9kΩ 1% resistor (0402)
R17	1	49.9kΩ 5% resistor (1206)
R4	1	100kΩ 1% resistor (0402)
R16	1	240kΩ 5% resistor (0603)
R23	1	10k Potentiometer (multi-turn) Bourn 3266W-1-103
SW1	1	Switch, Momentary, NO Mouser (101-0010)
U2	1	Op Amp, (SOT23-6) Maxim (MAX4238AUT)
U4	1	Serial 14 Bit DAC (10-pin µMAX®) Maxim (MAX5144EUB)
U1	1	Power Driver (20-Pin THIN QFN) Maxim (MAX8521ETP)

µMAX is a registered trademark of Maxim Integrated Products, Inc.
UCSP is a trademark of Maxim Integrated Products, Inc.
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