The ZXLD1321 is an inductive DC-DC converter, with an internal switch, designed for driving single or multiple LEDs in series up to a total of 1A output current.
Applications cover commercial environments with input voltages ranging from 1.2V to 12V.
The device employs a variable 'on' and 'off' time control scheme with adjustable peak switch current limiting and supports step-up (Boost) mode and self-powering Bootstrap operating modes, offering higher power efficiency and lower system cost than conventional PFM circuitry.
The device includes the DC-DC converter, a high-side current monitor and an NPN switching transistor to provide an integrated solution offering small PCB size, competitive cost/performance, high power efficiency of DC-DC conversion and maximum LED brightness/reliability.
More importantly, it retains design flexibility to add customer specific features.
The feedback control circuitry inside the ZXLD1321 provides excellent load and current regulation, resulting in very stable LED current over the useful life of the battery and over the full operating temperature range.
The LED current can be adjusted from 100% down to 10% of the set value by applying a dc voltage to the ADJ pin and down to 1% by applying a PWM signal to the ADJ pin.
An onchip LED protection circuit also allows output current to be reduced linearly above a predetermined threshold temperature using an external thermistor at the TADJ pin.
External resistors set nominal average LED current and coil peak current independently.
The device can be shut down by applying a continuous low level dc voltage to the ADJ pin.

• 1.2V to 12V Input voltage range
• Up to 1A output current
• Typical efficiency# >85%
• Bootstrap operation enables input voltage down to 1V
• User-defined thermal control of LED output current using external thermistor
• High output current stability over input voltage and temperature
• 12μA typical standby current
• LED current adjustable from 100% down to 2%
• Adjustable soft-start
• Drives up to 5 white LEDs in series

• High power LED flashlights
• LED back-up lighting
• General LED lighting
• Emergency lighting


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Advanced process capability and package design have been used to maximize the power handling and performance of this small outline transistor. The compact size and ratings of this device make it ideally suited to applications where space is at a premium

• High power dissipation SOT23 package
• 15A peak current
• Guaranteed gain at a collector current of 10A
• Very low saturation voltage

• MOSFET and IGBT gate driving
• Power switches
• Motor contro


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The ZXCT1032 is a high-side current monitor that drives a PMOS or PNP transistor to provide in-rush current limit and over-current protection. The ZXCT1032 includes a high accuracy high-side current monitor, a start-up timer and a re-try inhibit timer.
The ZXCT1032 takes the voltage developed across a current shunt resistor and compares
this with an externally set trip point. It works in three modes:
- Linear soft-start
- Over-current detector
- Over-current disconnect/fuse

Linear soft-start
Upon power up the ZXCT1032 enters a linear soft-start mode. During which the output current ramps up from zero to a maximum user defined trip point. The trip point is set by the voltage on ISET pin and RSENSE.
The ramp rate is determined by capacitor CT. The soft start ensures that capacitive loads are
smoothly charged without causing excessive power supply startup transients.

Over-current detectior
When external capacitor CT has charged up above the VISET the ZXCT1032 switches from its
soft-start mode to its over-current detection mode. During this mode the external MOSFET
will be fully enhanced reducing the its voltage drop and power dissipation.

• Accurate high-side current sensing
• User defined and dynamically adjustable trip current
• Load switch control
• Fault flag logic output
• User defined ramp and inhibit timers
• SO8 package
• Temperature range -40 to 85°C
While in this mode the internal current monitor continually checks the output current and compares it to the trip-current level determined by VISET.

Over-current disconnect/fuse
If the trip current limit is exceeded at any time the ZXCT1032 enters its Over-current disconnect
mode. The drive pin is driven high, turning the pass MOSFET off; the flag output goes low
indicating a fault.
The drive and flag outputs are latched in these states for a period determined by CT, VISET and the internally set discharge current (3µA typical). After CT has discharged to 80mV the ZXCT1032 will restart into its linear soft-start mode.
The CT charge and discharge times have been ratioed to so that the power dissipation in the
pass MOSFET should allow indefinite operation in the event of a continuous load failure.

Pin 3 description:
Determines the load current trip level or constant current level. ISET can be left open circuit (internal 2.1V reference) or driven via a DC voltage or µC PWM output. Its source impedance is 50k ohm

• Electronic fuse
• Short circuit protected supply feed
• Hot swap
• Power over twisted pair


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