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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. Resistor-
adjustable 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 (V
IN
+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° to +85° automotive temperature range.
C
C
Open-Drain Current-Limit Indicator Flag Constant PWM Frequency (400kHz)
Provides Easy
Filtering in Low-Noise Applications
2µA (max) Shutdown Current
-40° to +85° Temperature Range
C
C
Internal 1 (typ) 60V Switch
TM Technology Inc. reserves the right
P. 1
to change products or specifications without notice.
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