BL1084
BLOCK DIAGRAM
Fig 3. Block Diagram
DETAILED DESCRIPTION
BL1084 is a series of low dropout voltage three terminal regulators. Its circuit has a trimmed bandgap
reference to ensure output voltage accuracy independent of temperature variance. On-chip thermal shutdown
provides protection against overload and conditions as elevated ambient temperature.
Its application circuitry requires minimum number of external components. Both fixed voltage and
adjustable voltage versions need input and output capacitors to assure output voltage stability. Any desired
output voltage from 1.25V to 10V can be achieved with adjustable version by assigning proper values to two
external resistors in its application circuitry (as shown in Fig.4, as R1, R2 are the two external resistors.).
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TYPICAL APPLICATION
BL1084 has an adjustable version and fixed versions, Fig.4 shows their typical application circuitry.
A 10uF tan capacitor connected between input and GND as bypass capacitor and a 22uF tan capacitor
between output and GND are recommended for all application.
Using a bypass capacitor (CAdj) between the adjust terminal and ground can improve ripple rejection. The
bypass capacitor prevents ripple from being amplified in case the output voltage is increased. The impedance
of CAdj should be less than the resistance of R1 to prevent ripple from being amplified at any frequency. As
R1 is normally in the range of 120Ω~200Ω, the value of CAdj should satisfy the following condition:
1/(2* FrequencyRipple *Cadj)<R1
A 10µF tan capacitor is recommended.
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