BLUENRG-MSCSP datasheet(16/42 Pages) STMICROELECTRONICS

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Block diagram and descriptions

BlueNRG-MS

Name

Direction

Width

Description

SPI_IRQ

Out

Slave has data for master.

All the SPI pins have an internal pull-down except for the CSN that has a pull-up. All the

SPI pins, except the CSN, are in high impedance state during the low-power states. The

IRQ pin needs a pull-down external resistor.

The device embeds a battery level detector to monitor the supply voltage. The

characteristics of the battery level detector are defined in Table 19.

5.2

Power management

The BlueNRG-MS integrates both a low dropout voltage regulator (LDO) and a step-down

DC-DC converter, and one of them can be used to power the internal BlueNRG-MS

circuitry. However even when the LDO is used, the stringent maximum current

requirements, which are advisable when coin cell batteries are used, can be met and

further improvements can be obtained with the DC-DC converter at the sole additional cost

of an inductor and a capacitor.

The internal LDOs supplying both the 1.8 V digital blocks and 1.2 V digital blocks require

decoupling capacitors for stable operation. When the VBAT voltage is below 1.8 V, the

LDO 1.8 V output follows the VBAT value.

Figure 10 and Figure 11, show the simplified power management schemes using LDO and

DC-DC converter.

Figure 10: Power management strategy using LDO

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