UM1037 datasheet(16/46 Pages) STMICROELECTRONICS

16 / 46 page

Hardware layout and configuration

UM1037

16/46

Doc ID 18294 Rev 1

Configure ADC to measure voltage on IDD_measurement pin (PF3).

Configure LP_WAKEUP (PH5) as interrupt input on rising edge

Configuring IDD_CNT_EN (PH4) as output low level to start counting

Enter in Halt or active Halt mode

LP_WAKEUP rising edge wakeup the MCU after around 300ms

start ADC conversion as soon as possible after wakeup in order to measure the voltage

corresponding to halt mode memorised on 1uF capacitor (C5)

Reset the counter by programming IDD_CNT_EN High in less than 150 ms after the

wakeup to avoid 2 Kohm being connected later on VDD_MCU

In low power mode, the 2K resistor is connected when T4 goes off after entering in Halt

mode. Q12 output of the counter (U10) allows connection of the 2K resistor when the

current IDD becomes very low. The measurement timing is given below:

Figure 7.

STM8L1528-EVAL IDD low power mode measurement timing diagram

The low power mode measurement procedure can be used in Halt mode and slow or fast

active Halt modes if the IDD current doesn't exceed 30uA when VDD = 3.3 V or 15 µA when

VDD = 1.8 V else the Run measurement procedure need to be used up to 30 mA.

In low power mode the bias current of the operational amplifier input (U5 pin 4) is not

negligible compared to IDD current (Typical I bias is ~200 nA). To improve the IDD

measurement accuracy it is mandatory to subtract the I bias current to IDD measure since

this current isn't sink by the MCU. It is possible to measure I bias and to subtract this value

to MCU current. The procedure for precision IDD measurement is:

Place a jumper on JP4 pins 2 and 3

Follow the Halt mode procedure to measure I1 = I bias

Remove jumper JP4 pins 2 and 3 and place it on JP4 pins 1 and 2

Follow the Halt mode procedure to measure I2 = IDD + I bias

Calculate actual IDD: IDD = I2 - I1

2.16

IR LED & IR receiver

One IR LED LD7 is driven by either PA0 through two transistors T1 and T2 or PA0 directly

depending on setting of solder bridge SB7. One IR receiver is connected to PB2 which

shared by motor control connector through jumper JP15.

UM1037 Datasheet(PDF) 16 Page - STMicroelectronics