ES_LPC185X_3X_2X_1X_FLASH

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Errata sheet

Rev. 2.1 — 23 November 2012

8 of 11

NXP Semiconductors

ES_LPC185x/3x/2x/1x Flash

Errata sheet LPC185x/3x/2x/1x flash-based devices

4.

AC/DC deviations detail

4.1 IBAT.1: VBAT supply current higher than expected

Introduction:

The LPC185x flash-based devices contain a Real-Time Clock which measures the

passage of time. The RTC has an ultra-low power design to support battery powered

systems with a dedicated battery supply pin.

Problem:

On the LPC185x flash-based devices, high current consumption of about 70 uA or higher

may occur on the VBAT power supply pin due to current drain from the RTC_ALARM and

SAMPLE pins.

On the LPC185x flash-based devices, at temperatures lower than 0

C, high current

consumption up to 25 uA may occur on the VBAT power supply pin while VDD is present

if VDD < VBAT. This is seen during Deep Sleep, Power Down, and Deep Power Down

modes.

Work-around:

VBAT current consumption due to RTC_ALARM and SAMPLE pins can be lowered

significantly by configuring the RTC_ALARM pin and SAMPLE pins as "Inactive" by

setting the ALARMCTRL 7:6 field in CREG0 to 0x3 and the SAMPLECTRL 13:12 field in

CREG0 to 0x3. These bits persist through power cycles and reset, as long as VBAT is

present.

To work-around the current consumption at temperatures less than 0

C, keep the VBAT

voltage less than VDD. For example, use a 3.0 V VBAT voltage with a 3.3 V VDD supply.

This also avoids current consumption during active mode which can occur when VBAT >

VDD (see datasheet for details).

4.2 IRC.1: IRC frequency variation higher than expected

Introduction:

The IRC is used as the clock source for the WWDT and/or as the clock that drives the

PLLs and the CPU. The nominal IRC frequency is 12 MHz. The IRC is trimmed to 1 %

accuracy over the entire voltage and temperature range.

Problem:

On LPC185x flash-based devices, the IRC currently has a non-linear behavior at high

temperatures. This results in worse IRC accuracy than specified in the Data Sheet.

Work-around:

Many of the peripherals on these devices require use of an external crystal to meet timing

accuracy even at the specified accuracy. The IRC is typically used during boot up and

during UART and CAN In-Application Programming. It is recommended to avoid use of

UART and CAN IAP at elevated temperatures to ensure accuracy.