tm TE CH Create i7990N i7990N Boost Converter and Current Monitor for APD GENERAL DESCRIPTION The i7990N consists of a constant-frequency pulse-width modulating (PWM) step-up DC-DC converter with an internal switch and a current monitor with high-speed adjustable current limiting. This device can generate output voltages up to 60V and provides current monitoring up to 4mA (up to 240mW). The i7990N can be used for a wide variety of applications such as avalanche photodiode biasing, PIN biasing, and varactor biasing. The i7990N operates from 2.8V to 5.5V. The constant-frequency (400kHz), PWM architecture provides low-noise output voltage that is easy to filter. A high-voltage, internal power switch allows this device to boost output voltages up to 60V. Internal soft-start circuitry limits the input current when the boost converter starts. The i7990N features a shutdown mode to save power. The i7990N includes a current monitor with more than three decades of dynamic range and monitors current ranging from 500nA to 4mA with high accuracy. Resistoradjustable current limiting protects the APD from optical power transients. A clamp diode protects the monitor’s output from overvoltage conditions. Other protection features include cycle-by-cycle current limiting of the boost converter switch, undervoltage lockout, and thermal shutdown if the die temperature reaches +150°C. Applications • PIN/APD Biasing Supply and Monitoring. • Low-Noise Varactor Diode Bias Supplies. • SDH/SONET/Ethernet/FTTH/GPON Application. FEATURES Input Voltage Range +2.8V to +5.5V Wide Output-Voltage Range from (VIN+5V) to 60V 240mW Boost Converter Output Power Accurate ±5% (5:1) High-Side Current Monitor Resistor-Adjustable Ultra-Fast APD Current Limit The i7990N is available in a 3mm x 3mm, 16-pin QFN package and operates over the -40°C to +85°C automotive temperature range. Open-Drain Current-Limit Indicator Flag Constant PWM Frequency (400kHz) Provides Easy Filtering in Low-Noise Applications 2µA (max) Shutdown Current -40°C to +85°C Temperature Range Internal 1Ω (typ) 60V Switch TM Technology Inc. reserves the right P. 1 to change products or specifications without notice.