AT1309 Datasheet, PDF (9/14 Pages) Aimtron Technology – Micro-Power Step up DC-DC Converter

AT1309
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Function Description
The AT1309 is designed primarily for use in STN/OLED bias applications. The output
voltage of the step-up converter can be set from Vin to 26V with external resistive
voltage divider. The boost converter operates in current-mode PWM and a constant
frequency of 1.0 MHz. Depending on duty cycle of each switching cycle can regulate
output voltage. On the rising edge of the internal clock, the control and driver logic
block sets internal flip-flop when the output voltage is too low, which turns on the
N-MOS. The external inductor current ramps up linearly, storing energy in a magnetic
filed. Once peak current of inductor over trans-conductance output level, the N-MOS
turns off, the flip-flop resets, and external schottky diode turns on . This forces the
current through the inductor to ramp back down, transferring the energy stored in the
magnetic field to the output capacitor and load. To reduce external component amount,
the device will be built-in internal loop compensation.




Enable Control
Digital logic of EN provides an electrical ON/OFF control of the power supply.
Connecting this pin to ground or to any voltage less than 0.7V will completely turn
OFF the regulator. In this state, current drain from the input supply is less than 1µA,
the internal reference, error amplifier, comparators, and biasing circuitry turn off .
EN works as a simple on/off control. Drive EN high to enable the device, or drive EN
low for shutdown.




Soft-Start
Soft-start allows a gradual increase of the internal current-limit level for the step-up
converter during power-up to reduce input surge currents. As the internal current
source charges the internal soft-start capacitor, the peak N-MOS current is limited by
the voltage on the capacitor.
Cycle-by-Cycle Over-Current Protection
The AT1309 provides cycle-by-cycle over-current protection. Current limit is
accomplished using a separate dedicated comparator. The cycle-by-cycle current limit
abbreviates the on-time of the N-MOS in event that the current of flowing N-MOS is
greater than the current limit value. The current-limit feature protection against a hard
short or over-current fault at the output.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipation in the AT1309. When the
junction temperature exceeds Tj=130 Ċ, a thermal sensor activates the thermal
protection, which shuts down the IC, allowing the IC to cool. Once the device cools
down by 10 Ċ, IC will automatically recover normal operation. For continuous
operation , do not exceed the absolute maximum junction-temperature rating of
Tj=120 Ċ.




7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: [phone] Fax: [phone]
WWW: http://www.aimtron.com.tw
3/2/2006 REV:1.1
Email: [e-mail]
9