Electronic Components Datasheet Search |
|
AD9660 Datasheet(PDF) 9 Page - Analog Devices |
|
AD9660 Datasheet(HTML) 9 Page - Analog Devices |
9 / 12 page AD9660 REV. 0 –9– Example Calculations The example below (in addition to the one included in the sec- tions above) should guide users in choosing RGAIN, CGAIN, the hold capacitor values, and worst case calibration times. System Requirements: • Bias laser power: 4 mW Bias ± 5% • Write laser power: 25 mW ± 0.5% • Bias Hold Time: 1 ms • Write Hold Time: 1 µs Laser diode/photo diode characteristics: • Laser efficiency 0.5 mA/mA • Monitor current: 5 µA/mA • From the laser power requirements and efficiency we can estimate: ∆I BIAS MAX = 4 mW × (5% ) / 0. 5 mW mA = 400.0 µA and ∆I WRITE MAX = 25 mW × 0. 5% ( ) /0.5 mW mA = 250 µA • Choosing hold caps based on these: C BIAS HOLD = 18 ×10 −9 ×1ms 400 µA = 0.045 µF and C WRITE HOLD = 18 ×10 −9 ×1µs 250 µA = 72 pF • The bias loop initial calibration time for a <1% error: 5 τ = 5 × RC = 5 × 550 Ω × 0.045 µF = 123.75 µs • Bias loop recalibration for a 1% error after 5% droop (need to correct within 20%): 2 τ = 2 × RC = 2 × 140 Ω × 0.045 µF = 12.6 µs • The write loop initial calibration time for <0.1% error: 7 τ = 7 × RC = 7 × 550 Ω × 72 pF = 277.2 ns • Write loop re-calibration for a 0.1% error after 0.5% droop (need to correct within 20%): 2 τ = RC = 2 × 140 Ω × 72 pF = 20.2 ns • From the monitor current specification and the max power specified: I MONITOR MAX = 25 mW 5 µA mW = 125 µA and R GAIN = 1.6 V 1.85 × I MONITOR MAX − 50 Ω= 6.9 kΩ • C GAIN would be chosen as 2 pF (see Table I). Driving the Analog Inputs The BIAS LEVEL and WRITE LEVEL inputs of the AD9660 drive the track and hold amplifiers and allow the user to adjust the amount of output current as described above. The input voltage range on both inputs is VREF to VREF + 1.6 V, requiring the user to create an offset of VREF for a ground based signal. The circuit in Figure 9 will perform the level shift and scale the output of a DAC whose output is from ground to a positive voltage. This solution is attractive because both the DAC and the op amp can run off a single +5 V supply, and the op amp doesn’t have to swing rail to rail. DAC1 DAC2 VDAC1 VDAC2 OP291 OP291 +5V VREF + VDAC1 = VBIAS LEVEL R2 R1 VREF + VDAC2 = VWRITE LEVEL R4 R3 BIAS LEVEL VREF WRITE LEVEL AD9660 R1 R2 R3 R4 R3 R4 R1 R2 Figure 9. Driving the Analog Inputs |
Similar Part No. - AD9660 |
|
Similar Description - AD9660 |
|
|
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 |