EA-QSB-015 Embedded Artists, EA-QSB-015 Datasheet - Page 8

• Manufacturer Part Number: EA-QSB-015
• Description: Development Boards & Kits - ARM QUICK START BOARD LPC11U35
• Manufacturer: Embedded Artists

Specifications of EA-QSB-015

• Rohs: yes
• Product: Development Kits
• Tool Is For Evaluation Of: LPC11U35
• Core: ARM Cortex M0
• Interface Type: USB
• Operating Supply Voltage: 3.3 V

Copyright 2012 © Embedded Artists AB
LPC11U35 QuickStart Board - User’s Guide
3 Schematic
This chapter contains detailed information about the electrical and mechanical design of the
LPC11U35 QuickStart Board. The schematic can be downloaded in pdf format from the support page,
and is recommended to have printed out while reading this chapter.
3.1
The board is powered either via the USB interface or from an external +5V supply. U2 is an on-board
voltage regulator capable of creating a +3.3V voltage for the LPC11U35. It can deliver up to 150 mA.
The LPC11U35 itself does not consume that much so there is at least 100mA available for external
circuit use.
If an external +5V supply is used, it shall be stable with less than 50mV noise. Input supply voltage
should not exceed +5.5V since this is the maximum allowed voltage on the LPC11U35 VBUS pin.
Technically it is possible to have higher voltage on the external supply since the VBUS pin is
connected via a 2Kohm resistor. The input protection diodes on the VBUS pin will clamp the voltage to
+5.5V. Under no circumstances should the input voltage exceed 16V, which is the maximum input
voltage for the voltage regulator, U2. See the datasheet for details.
3.2
The microcontroller unit (MCU), U1, is the LPC11U35 from NXP. It contains a Cortex-M0 core that can
operate at frequencies up to 50 MHz. Internal PLL:s can create the core clock of 48 MHz from the
external 12.0000 MHz crystal. A USB clock reference of 48 MHz can also be created this way.
The LPC11U35 contains a lot of different peripheral units. See the LPC11U35 User’s Manual [2] for
details about the peripherals, clock and power control.
3.3
The reset generation is handled by a voltage supervisor chip, MIC6315-29D3U from Micrel. The reset
signal will be held active (i.e., low) until the supply voltages, +3.3V, is within margins (above 2.93V).
The reset duration is typically 200 mS (consult the MIC6315-29D3U datasheet for exact details). The
output reset signal is open-drain so a pull-up resistor is needed (R15). There is a reset-LED that lights
when reset is active.
An external reset source can pull the reset signal low (with an open-collector/open-drain output).
There is also a reset push-button (SW1) for manual triggering of a reset pulse.
3.4
Further, there is a LED connected to pin PIO0_7. A 2Kohm resistor limits the diode current to about
0.9mA. The LED will light when PIO0_7 is high. The PIO0_7 pin is a high-drive output capable of
supplying up to 20 mA. See the datasheet for details.
3.5
The LPC11U35 has an on-chip USB Device interface. This interface is supported on-board via a mini-
B USB connector, J3. There is also a USB connect functionality to connect a 1.5Kohm resistor to the
USB-DP signal. This functionality also has LED indication. The board is typically powered via the USB
interface.
The USB interface is protected by ESD protection diode, D1.
Note that if USB-ISP mode is activated, it is possible to download firmware into the LPC11U35 via the
USB interface.
Powering
LPC11U35 MCU
Reset Generation
LED on PIO0_7
USB Interface
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