BL654 datasheet(33/60 Pages) LSTD

33 / 60 page

https://www.lairdconnect.com/wireless-

modules/bluetooth-modules/bluetooth-5-

modules/bl654-series-bluetooth-module-nfc

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The BL654 supports readback protection capability that disallows the reading of the memory on the nrf52840 using a JTAG

interface. Available via smartBASIC or the Nordic SDK.

The BL654 offers a range of functions for generating public/private keypair, calculating a shared secret, as well as generating an

authenticated hash. Available via smartBASIC or the Nordic SDK.

This is not required for normal BL654 module operation.

The BL654 uses the on-chip 32.76 kHz RC oscillator (LFCLK) by default (which has an accuracy of ±500 ppm) which requires

regulator calibration (every eight seconds) to within ±500 ppm.

You can connect an optional external high accuracy (±20 ppm) 32.768 kHz crystal (and associated load capacitors) to the

BL654SIO_01/XL2 (pin 41) and SIO_00/XL1 (pin 42) to provide improved protocol timing and to help with radio power

consumption in the system standby doze/deep sleep modes by reducing the time that the RX window needs to be open. Table

23 compares the current consumption difference between RC and crystal oscillator.

Table 23: Comparing current consumption difference between BL654 on-chip RC 32.76 kHz oscillator and optional

external crystal (32.768kHz) based oscillator

BL654 On-chip 32.768 kHz RC Oscillator

(±500 ppm) LFRC

Optional External Higher Accuracy (±20

ppm) 32.768 kHz Crystal-based Oscillator

LFXO

Current Consumption

of 32.768 kHz Block

0.7 uA

0.23 uA

Standby Doze Current

(SYSTEM ON IDLE +full

RAM retention +RTC

run current + LFRC or

LFXO)

3.1 uA

2.6 uA

Calibration

Calibration required regularly (default eight

seconds interval).

Calibration takes 33 ms; with DCDC used, the

total charge of a calibration event is 16 uC.

The average current consumed by the

calibration depends on the calibration interval

and can be calculated using the following

formula:

CAL_charge/CAL_interval

– The lowest

calibration interval (0.25 seconds) provides an

average current of (DCDC enabled):

16uC/0.25s = 64uA

To get the 500-ppm accuracy, the BLE stack

specification states that a calibration interval of

eight seconds is enough. This gives an

average current of:

16uC/8s = 2 uA

Added to the LFRC run current and Standby

Doze (IDLE) base current shown above results

Not applicable

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