L1806G-SH2-R Datasheet, PDF (7/7 Pages) Unisonic Technologies – With internal Soft-Start

L1806
CMOS IC
 APPLICATION INFORMATION
1. Power Sequencing
When there’s no main voltage applied at V_IN, it is suggested not to apply a voltage to V_OUT for a long time.
Because the internal parasitic diode (between V_OUT to V_IN) will conduct and dissipate power, there’s no protection.
2. Output Capacitor
A proper output capacitor to maintain stability and improve transient response over temperature and current is
necessary. Proper ESR (equivalent series resistance) and capacitance of the output capacitor should be selected
properly for stability of the normal operation and good load transient response.
Many kinds of capacitors can be used as an output capacitor, such as ultra-low-ESR capacitors (like ceramic
chip capacitors), low-ESR bulk capacitors (like solid Tantalum, POSCap, and Aluminum electrolytic capacitors). And
also the value of the output capacitors’ can be increased without limit.
In the applications with large stepping load current, the low-ESR bulk capacitors are normally recommended.
Decoupling ceramic capacitors are recommended to be placed at the load and ground pins very closely and also
the impedance of the layout must be minimized.
3. Input Capacitor
In order to prevent the input rail from dropping, the proper input capacitor to supply current surge during stepping
load transients is required. Because the limited slew rate of the surge currents, more parasitic inductance needs more
input capacitance.
Ultra-low-ESR capacitors (>100mF, ESR<300mW) is recommended for the input capacitor.
4. Feedback Network
The following figure shows the feedback network between V_OUT GND and FB pins. Working with the internal error
amplifier, the feedback network can provide proper frequency response for the UTC L1806.
V_ERR
EAMP
V_REF
V_OUT
FB
V_FB
R1 _C1
R2
V_OUT
ESR
C_OUT
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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