DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller
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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 1

High-Speed Current Mirror and Integrated FETs for DC-DC Controller General Description The DS3922 high-speed current mirror integrates highvoltage devices necessary for monitoring the burst mode receive power signal in avalanche photodiode (APD) biasing and OLT applications. The device has two small and one large gain current mirror outputs to monitor the APD current. An adjustable current clamp limits current through the APD. The clamp also features an external shutdown. An integrated FET is also provided that can be used with an external DC-DC controller to create a high-voltage boost DC-DC converter. Integrated low-voltage FET circuits can be used to create buck, boost, and inverting DC-DC converters for efficient laser bias and EML bias applications. The DS3922 is available in a 24-pin TQFN package and operates over an extended -40°C to +95°C temperature range. TEMP LIMIT CURRENT LIMIT EML NEGATIVE BIAS INVERTING SWITCHER LVIN2 LVCC LVCC pMOS MIRIN MIROUT ● Low-Voltage Synchronous Buck FETs for Efficient DFB Bias ● Low-Voltage pMOS FET for Generating Negative Bias Voltage for EMLs ● External Capacitor Connection for Controlled RC Time Constant of APD Voltage Filter ● Current Clamp with Adjustable Limit and External Shutdown with Limit Status ● Two Current Mirror Outputs and Additional SmallSignal Current Mirror Output for ADC Measurement Avalanche Photodiode (APD) Biasing GPON OLT 10GPON OLT EML Bias 10G EPON ● High-Voltage Switch FET for Boost DC-DC Converter HIGH-VOLTAGE AND MIRROR CIRCUITS Applications LOW-VOLTAGE FET CIRCUITS LVCC ● Supports -32dBm to -5dBm Optical Input Range with ±0.5dB Accuracy ● 24-Pin (3.5mm x 3.5mm) TQFN Package with Exposed Pad Block Diagram LVOUT2 (-3.7V TO LVCC) OPEN-DRAIN pMOS EML, DFB, APC HIGH-EFFICIENCY BIAS LVIN1 LVCC LVCC pMOS nMOS LVGND NONOVERLAP DRIVER Ordering Information appears at end of data sheet. For related parts and recommended products to use with this part, refer to www.maximintegrated.com/DS3922.related.

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 2

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (VMIRIN = 15V to 76V, VCC = 2.85V to 3.63V, TA = -40°C to +95°C, unless otherwise noted.) (Note 2) PARAMETER...

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 3

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Electrical Characteristics (continued) (VMIRIN = 15V to 76V, VCC = 2.85V to 3.63V, TA = -40°C to +95°C, unless otherwise noted.) (Note 2) PARAMETER Maximum MIROUT Current SYMBOL ICLAMP ISRC/SHDN = high MIROUT Capacitive Load Total capacitance on MIROUT to achieve accuracy specification ILIMS Output Time IOUT-to-MIROUT Ratio KIOUT, KVIP1, and KVIP2 Voltage Variation Logic Output Levels: ILIMS Mirror Voltage-Drop Monitor Load Capacitance External capacitance required on APDV Mirror Voltage-Drop Monitor Output Voltage Variance...

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 4

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Low-Voltage FET Parameters (VLVCC = 2.85V to 3.63V, TA = -40°C to +95°C, unless otherwise noted.) (Note 2) PARAMETER LVFET1P On-Resistance Note 2: Limits are 100% tested at TA = +25°C. Limits over the operating temperature range and relevant supply voltage rating are guaranteed by design and characterization. Note 3: ISRC/SHDN: Not connected. HV FET: 250kHz driven by 100Ω source with 2.97V square wave. HVD connected to GND. Note 4: External resistor connected to GND. This value guarantees accuracy of the DS3922. Note 5:...

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 5

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) CURRENT MIRROR RATIO vs. MIROUT CURRENT CURRENT MIRROR RATIO CURRENT MIRROR FILTER FREQUENCY RESPONSE

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 6

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Analog 3.3V (Nominal) Supply 20% Current Mirror Output. Connect to resistor to ground. 80% Current Mirror Output. Connect to resistor to ground. 10% Current Mirror Output. If not used, do not connect. Digital Input. Connect to an external PWM output to create buck DC-DC converter. Controls output LVOUT1. Push-Pull Output Open-Drain pMOS Output. This output does not have a diode connection to LVGND and can go a few volts below LVGND for inverter application. Digital 3.3V (Nominal) Supply Low-Voltage Supply Voltage Low-Voltage...

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 7

High-Speed Current Mirror and Integrated FETs for DC-DC Controller FUNCTION Dual-purpose pin: ISRC: A resistor connected to this pin controls the amount of current flowing through a current source connected to MIROUT. Note: During this mode of operation, the microcontroller pin (if connected) should be high impedance. SHDN: If pulled high, sets MIROUT to high impedance. Current-Limit Status. Active-low signal indicating that the current-limit threshold is exceeded. APD Voltage Monitor. Provides output voltage used to calculate the voltage on the APD. Resistor Limit. Connect resistor between...

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 8

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Typical Application Circuit PWM APDV IOUT R8 5kΩ LVCC ILIMS ISRC/SHDN

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DS3922 High-Speed Current Mirror and Integrated FETs for DC-DC Controller - 9

High-Speed Current Mirror and Integrated FETs for DC-DC Controller Detailed Description Current Mirror Filter The DS3922 contains discrete high-voltage (HV) components required to create an APD bias voltage and to monitor the APD bias current. The device’s mirror outputs are a current that is a precise ratio of the output current across a large dynamic range. The mirror response time is fast enough to comply with GPON Rx burst-mode monitoring requirements. The device has a built-in current-limiting feature to protect APDs. This current limit is adjustable using an external resistor. The APD...

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