Zakładka z wyszukiwarką danych komponentów |
|
ADL5317-EVAL Arkusz danych(PDF) 9 Page - Analog Devices |
|
ADL5317-EVAL Arkusz danych(HTML) 9 Page - Analog Devices |
9 / 16 page ADL5317 Rev. 0 | Page 9 of 16 THEORY OF OPERATION The ADL5317 is designed to address the need for high voltage bias control and precision optical power monitoring in optical systems using avalanche photodiodes. It is optimized for use with the Analog Devices, Inc. family of translinear logarithmic amplifiers that take advantage of the wide input current range of the ADL5317. This arrangement allows the anode of the photodiode to connect directly to a transimpedance amplifier for the extraction of the data stream without need for a separate optical power monitoring tap. Figure 19 shows the basic connections for the ADL5317. 1 FALT 2 VSET 3 4 11 IPDM 12 NC 10 NC 9 GARD 5 6 7 8 15 16 14 13 ADL5317 FALT VSET VPLV VPHV MIRROR CURRENT OUTPUT 0.01 μF APD 1nF 1k Ω IAPD 0.1 μF 0.01 μF HIGH VOLTAGE SUPPLY 0 Ω LOW VOLTAGE SUPPLY 10k Ω 0 Ω 0.01 μF 0.1 μF Figure 19. Basic Connections At the heart of the ADL5317 is a precision attenuating current mirror with a voltage following characteristic that provides precision biasing at the monitor input. This architecture uses a JFET-input amplifier to drive the bipolar mirror and maintain stable VAPD voltage, while offering very low leakage current at the VAPD pin. The mirror attenuates the current sourced through VAPD by a factor of 5 to limit power dissipation under high voltage operation and delivers the mirrored current to the IPDM monitor output pin. Proprietary mirroring and cascoding techniques maintain the linearity vs. the input current and stability of the mirror ratio over a very wide range of supply and VAPD voltages. BIAS CONTROL INTERFACE In the linear operating mode, the voltage at VAPD is referenced to ground, and follows the simplified equation VAPD = 30 × VSET GARD is driven to the same potential as VAPD for use in shielding the highly sensitive VAPD pin from leakage currents. The GARD and VAPD pins are clamped to within approxi- mately 40 V below the VPHV supply to prevent internal device breakdowns, and VAPD is clamped to within a volt of GARD. The VAPD adjustment range for a given high voltage supply, VPHV, is limited to approximately 33 V (or less, for VPHV < 41 V). For example, VAPD is specified from 40 V to 73.5 V for a 75 V supply, and 6 V (the minimum allowed) to 28.5 V for a 30 V supply. When VAPD is driven to its lower clamp voltage via the VSET pin, the mirror can continue to operate, but the VAPD bias voltage no longer responds to incremental changes in VSET. GARD INTERFACE The GARD pins primarily shield the VAPD trace from leakage currents and filter noise from the bias control interface. GARD is driven by the VSET amplifier through a 20 kΩ resistor. This resistor forms an RC network with an external capacitor from GARD to ground that filters the thermal noise of the amplifier’s feedback network and provides additional power supply rejection. The series components, RCOMP and CCOMP, shown in Figure 20, are necessary to ensure essential high frequency compensation at the VAPD input pin over the full operating range of the ADL5317. VSET AMPLIFIER GARD CGRD ADL5317 X30 VAPD CCOMP RCOMP 20k Ω Figure 20. Filtering VAPD Using the GARD Interface The cutoff frequency of the GARD interface for small signals and noise is defined by GRD 3dB C F × × = kΩ 20 2π 1 where: F3dB is the cutoff frequency of the low-pass filter formed by the on-board 20 kΩ and CGRD. CGRD is the filter capacitor installed from GARD to ground. A larger value for CGRD (up to approximately 0.01 μF) provides superior noise performance at the lowest input current levels, but also slows the response time to changes in VSET. The pull-up of the VSET amplifier is limited to approximately 2.5 mA, resulting in a slew limited region for large signals, followed by an RC decay for the final 700 mV. This decay corresponds to the above single-pole equation. The pull-down of the VSET amplifier is largely resistive, equivalent to approximately 90 kΩ in parallel with 70 μA to ground. |
Podobny numer części - ADL5317-EVAL |
|
Podobny opis - ADL5317-EVAL |
|
|
Link URL |
Polityka prywatności |
ALLDATASHEET.PL |
Czy Alldatasheet okazała się pomocna? [ DONATE ] |
O Alldatasheet | Reklama | Kontakt | Polityka prywatności | Linki | Lista producentów 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 |