L9780 datasheet(12/56 Pages) STMICROELECTRONICS

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Main functionalities

L9780

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DocID026356 Rev 3

Main functionalities

4.1

Power supplies

4 different power supplies are present in the device: VCCA, VCCD, VCCCP, VCCI,

respectively for analog part, digital part, charge pump, digital interfaces. Digital inputs are

compatible with 2 different logic levels (5 V or 3.3 V, the possible levels for VCCI), and are

converted to the range 0V-VCCD using internal level shifters connected to VCCD and VCCI.

In the device a negative charge pump is also present and it is used to generate -5 V voltage

level (on CP pin), to bias the substrate and to allow the excursion to the negative range to

the output pins of VCCS. Charge pump clock frequency is 2 MHz.

3 different ground pins are also present in the device: GNDA, GNDD, GNDCP, respectively

for analog, digital and charge pump circuitry.

Possible ranges for power supplies, currents consumption and input/output logic levels are

specified in Table 9, Table 12 and Table 13. External component values are specified in

Table 19.

4.2

Pin protection

On the device a high ESD reference voltage pin (VESD) is available and is used as a

protection for the pins externally connected to the sensor and for HD pin; this voltage must

be the highest in the application and has to be always connected to the device, through the

RC low pass filter shown in Figure 12 (external component values are specified in Table 19).

For pins compatible to negative voltages, the negative ESD reference voltage is the

substrate (internally connected to CP pin, -5 V). All the other pins have a 5V positive ESD

protection voltage level and GND as negative ESD protection voltage level.

4.3

Internal references

Into the device the following voltage references are present:

–

a band-gap voltage (typical value 1.215 V) with 3 trimming bits dedicated;

–

REF voltage; obtained as the band-gap multiplied by a factor of 1.555; typical

value for this voltage is 1.89 V (possible range for this parameter is specified in

Table 10.

–

REF2 voltage; typical value is about VCCA/2 (possible range for this parameter is

specified in Table 11).

All internal currents are generated from a reference current obtained by the band-gap

(buffered on BG pin) applied on an external resistance; the possible BG pin voltage range is

specified in Table 9, the value of external resistance is defined in Table 19.

All timing references are calculated as multiples of the period of the internal oscillator

(TOSC); the typical oscillation frequency is 4 MHz, the possible range is specified in

Table 15. Internal oscillator has 4 trimming bits dedicated.

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