A1085
AiT Semiconductor Inc.
www.ait-ic.com
3A LOW-DROPOUT POSITIVE VOLTAGE REGULATOR
THERMAL SHUTDOWN AND CURRENT LIMIT FUNCTIONS
DETAILED INFORMATION
The A1085 is a series of low dropout voltage, three terminal regulators which application circuit of fixed
version only needs two capacitors and the adjustable version only needs two resistors and two capacitors to
work. It is composed of some modules including start-up circuit, bias circuit, band-gap, thermal shutdown,
current limit, power transistors and its driver circuit and so on.
Thermal Shutdown and Current Limit
The A1085 thermal shutdown and current limit modules can assure chip and its application system working
safety when the environment temperature is larger than 140oC or output current is larger than 3.2A.
Stable Reference Output Voltage
The band-gap module provides stable reference voltage, whose temperature coefficient is compensated by
careful design considerations. The temperature coefficient is under 100ppm/oC. And the accuracy of
output voltage is guaranteed by trimming technique.
Application Hints
See Schematic 1
1. Recommend 10uF Tan capacitor (CIN) as bypass capacitor for all application circuit.
2. Recommend 22uF Tan capacitor (COUT) to assure circuit stability.
3. Using a bypass capacitor (CADJ) between the adjust terminal and ground can improve ripple rejection, this
bypass capacitor prevents ripple from being amplified as the output voltage is increase. The impedance
of CADJ should be less than the resistor’s (R1) which is normally in the range of 120Ω ~ 200Ω, the value of
CADJ should satisfy this equation: 2 x FRIPPLE x ＜R1. Recommend using 10uF Tan capacitor.
Output Voltage of Adjustable Version
The A1085-ADJ adjustable version provides 1.25V reference voltage. Any output voltage between 1.25V ~
13.8V can be available by choosing two external resistors (connection method is shown in Schematic 1), R1
and R2 are the two external resistors.
REV1.2
-AUG 2006 RELEASED – SEP 2008 REVISED -
- 7 -
AITSEMI [ AiT Semiconductor ]
