Electronic Components Datasheet Search |
|
MAX3970D Datasheet(PDF) 5 Page - Maxim Integrated Products |
|
MAX3970D Datasheet(HTML) 5 Page - Maxim Integrated Products |
5 / 10 page 10Gbps, 3.3V Low-Power Transimpedance Amplifier with RSSI _______________________________________________________________________________________ 5 Detailed Description The MAX3970 transimpedance amplifier is optimized for 10Gbps fiber optic receivers. Figure 1 is a function- al diagram of the MAX3970, which comprises a tran- simpedance amplifier, a voltage amplifier, an output buffer, a received-signal strength indicator, and a DC- cancellation circuit. Transimpedance Amplifier Photodiode signal current flows into the summing node of a high-gain amplifier. Shunt feedback through RF converts this current into a voltage with a gain of approximately 400 Ω. Schottky diodes clamp the output voltage for large input currents, as shown in Figure 2. Voltage Amplifier The voltage amplifier converts single-ended signals to differential signals and introduces approximately 4dB of gain. Output Buffer The output buffer is optimized to drive a 100 Ω differential load between OUT+ and OUT-. Although short-circuit protection is provided, this stage will not drive a 50 Ω load to ground. For proper operation, the load must be AC-coupled. For large signals, the output buffer produces a limited, 500mVP-P differential output voltage. Terminate the MAX3970 outputs differentially for optimum supply-noise rejection. If a single-ended output is required, terminate the used and unused outputs similarly. DC Cancellation Circuit The DC cancellation circuit centers the input signal within the transimpedance amplifier’s linear range (Figure 3). Low-frequency feedback is employed to remove the input signal’s DC component. The DC cancellation circuit is internally compensated and therefore does not require external capacitors. This circuit minimizes pulse-width distortion for data sequences that exhibit a 50% mark density. A mark density significantly different from 50% will cause the MAX3970 to generate pulse-width distortion. Received-Signal Strength Indicator The received-signal strength indicator (RSSI) provides a voltage proportional to the DC input current. The RSSI circuitry is designed to drive a 10k Ω load and is used during the assembly process to optimally align the pho- todiode. The lowpass filter in the DC cancellation circuit determines the response time of the RSSI circuit. Design Procedure Power Supply The MAX3970 requires wide-band power-supply decoupling. Power-supply bypassing should provide low impedance between VCC and ground for frequen- cies between 50kHz and 10GHz. Use LC filtering at the main supply terminal and decoupling capacitors as close to the die as possible. PAD NAME FUNCTION BP1, BP2, BP18 VCC1 Power Supply. Provides supply voltage to input circuitry and bias to the photodiode via an internal 410 Ω resistor. BP3 FILTER Provides bias voltage for the photodiode through a 410 Ω resistor to VCC1. When grounded, this pin disables the DC cancellation circuit to allow a DC path from IN to OUT+ and OUT- for testing. BP4 TEST Test Pad. This pad is connected to IN via a 1k Ω resistor. BP5 IN Amplifier Input. Accepts photodiode input current. BP6, BP7 GND1 Ground BP8, BP9 GND2 Ground BP10, BP13 GND3 Ground BP11 OUT- Negative CML Output. Current flowing into IN causes OUT- to decrease. BP12 OUT+ Positive CML Output. Current flowing into IN causes OUT+ to increase. BP14, BP15 BP16 VCC2 Power Supply. Provides supply voltage to the output buffers. BP17 RSSI Received-Signal Strength Indicator. This pin provides a voltage proportional to the DC input current. Monitor this output during assembly to optimally align the photodiode to the optics. Pad Description |
Similar Part No. - MAX3970D |
|
Similar Description - MAX3970D |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |