It is simply for voltage regulation.
Do you know, voltage of USB Vbus is not always 5.0v
When relay via USB Hub, the voltage down to 4.0v occasionally.
So, LDO will regulate these voltage to stable.
Are you working with your own board or with a cypress kit if so which kit is it?
Hello, thank you PSoC73 for your answer. I unsterstand. I know that the USB_PORT is not always 5 V. But I thought that the LDO need a voltage for example 5.5 V to convert . And if it gets a lower voltage it does nothing. @zeta I use the CY8CKIT-050 PSoC® 5LP Development Kit (http://www.cypress.com/?rID=51577) to get in contact with Cypress 5LP. But now I want to make my own kit. This kit should be the controller for ADC/DAC/CAN applications. The concept from Arduino. The board should be very simple. Just the CY8C5868AXI-LP035 and maybe CY7C68015A-56LTXC (For program the Cy8 via Bootloader or USSP if I understand how it works). Now I use my reply to ask a second question about the Development Kit Schematic. What is the funktion of the 10 Pin trace header J40 (P2 - P2. Is it to program the chip? Best regards, Flo
A "typical" LDO needs anywhere from sub 100 mV to 300 mV to keep
its output at the regulation point. However the AP1117, which supplies
Vbus, has a droput > 1V, consult spec sheet. Looks more like a non-
LDO to me.
This is a linear lDO, so when regulator is in droput, the output drops
linearly with input V. So if dropout is 1.3V, and input to LDO is at 5.0
V, then its output, essentially saturated, is at 3.7 V.
Compounding this is a schottky is used on LDO in to insure no reverse
current flows back into LDO input, otherwise LDO could be damaged
and or USB physical interface. This diode further aggravates dropout
The 10 pin header, from the board manual -
4.2.2 Programming Interface
This kit allows programming in two modes:
■ Using the on-board programming interface
Using the JTAG/SWD programming interface with a MiniProg3
188.8.131.52 JTAG/SWD Programming
Apart from the on-board programming interface, the board also provides the option of using the
MiniProg3. This interface is much faster than the on-board program interface. The JTAG/SWD
programming is done through the 10-pin connector, J3.
Hi everybody, first Dana thanks for your answer. I know that programming use JTAG/SWD with J3 is possible. But my question was about J40. This port is connected with port 2-2 VDD and Ground. The "Development Kit Guide" report only that the ports are connected with the J40. I couldn´t find something in the datasheet of CY8C5868AXI-LP035 about a special funktion with this Ports. So what is the reason for J40? Is this header to record something while the program is running? Or if I write something to the board included display I get it on my computer, too. With port J40, a programm and MiniProg? Thanks everybody for your help! Best regards, Flo
And sorry a third questions. How can I get heels :-)? Best regards, Flo