Improving the power scheme of the wireless keyboard

My friend had a problem with the wireless keyboard - the batteries quickly ran out in it.
Moreover, when they sat down, she could work for a long time, but the "range" was sharply reduced to complete inability. And the other day I just decided to try an excellent microcircuit - NCP1402. I showed my friend her capabilities, and he got the idea to use it to solve problems with the keyboard power.


For details - please, under cat.

The chip is a step-up DC-DC converter, highly efficient and requiring a minimum of “body kit”. At the input you need to apply a voltage of 0.8 volts. At the same time, the manufacturer claims that, having started, the converter will work until the battery drops to 0.3 volts, if it is not disconnected. It is available in versions:

NCP1402SN19T1 (1.9 V at the output)
NCP1402SN27T1 (2.7 V)
NCP1402SN30T1 (3.0 V)
NCP1402SN33T1 (3.3 V)
NCP1402SN50T1 (5.0 V)

I bought 10 pieces of NCP1402SN33T1 per sample (a price of about 30 rubles).

Obviously, the problem with the keyboard was a drop in battery voltage, which became insufficient to maintain the keyboard's previous range. It was decided to upgrade the power scheme. The body kit includes:
  • Schottky diode, the most important component in terms of characteristics, for the efficient operation of the converter. The datasheet indicates the requirements. I used MBR0520LT1G in the SOD123 package
  • 47uH inductor. I used LQH32MN470K23L, SMD1210
  • 10uF input capacitor, ceramic, SMD0805
  • 2 output capacitors at 22uF, ceramic, SMD1206


There is a nuance with the wiring of the board - for maximum efficiency it is better to make the shortest paths possible. But already I wanted compactness - we decided to put the board in the place in the keyboard reserved for storing the usb receiver.

Wiring was done in Proteus ARES.
I post the pdf for LUT : dl.dropbox.com/u/36371114/ncp1402layout.pdf I

etched the board, cut it, made the installation of components using lukey702 and hands :)
The board size turned out 12x14mm.



Testing - we connect 1 or 2 AAA batteries - at the output - the coveted 3.3 volts.
We put in the keyboard:



We rejoice in excellent range even on 1 battery.

PS put one AAA battery, it has been working for a week, without turning it off. The voltage did not drop, the current without pressing the keys is 89µA.

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