L9001 datasheet(16/38 Pages) STMICROELECTRONICS

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Power supply

L9001

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DS12089 Rev 2

5.3

VDD2 regulator

The device integrates a second configurable BUCK/LDO regulator VDD2, whose output

voltage can be adjusted between 0.8 V and 5 V and so it can be adapted to supply uC core

voltage.

The BUCK/LDO mode can be selected through CONF2 pin as described in Section 5.1; the

current capability depends on the chosen option and is specified in Table 10.

The output voltage can be adjusted by adequately sizing the external divider in order to

have the specified feedback reference voltage on the FB2 input pin.

The input voltage of VDD2 regulator is VR1 and this input can be connected to:



VS supply voltage, in a configuration in which VDD2 is directly supplied from battery;



VDD1 output, in a configuration in which VDD2 is supplied by VDD1 pre regulator.

The connection of VR1 to VS battery will automatically disable VDD1 (as explained in the

previous section) as the device does not allow the independent operation of VDD1 and

VDD2 both supplied from battery. As a consequence, when both regulators are operating,

the external load applicable on VDD1 is 1 A reduced by the input current of VDD2 regulator.

When VDD2 regulator input is connected to VS supply, the output voltage in buck mode

cannot reach voltages lower than 2.5 V, whereas there are no limitations in LDO mode.

The output voltage of VDD2 regulator (which is generated by the buck or directly V20 in

case of LDO mode) can be directly used by external loads and must be connected also to

pin VR2. In fact VR2 is the output of a LDO bypass regulator which is used to keep

regulation active when output current demand decreases below a specified threshold

ILIM_BP2 (bypass mode). In this bypass mode, the reference feedback voltage FB2 is

regulated according to the FB2_byp parameter. Such mode is used for example when the

system needs to reduce the overall consumption by entering the Low Power mode (see

dedicated Section 8.2.4 for details)

To guarantee full flexibility in the system power supply architecture, VDD2 regulator can also

be disabled, if application does not require it. This can be done by shorting the FB2 output

pin to VS.

Lout1

Inductor at VR1

Application info

μH

ESR_Cout1

Eq. series resistance for

Cout1

Application info

mΩ

Cvs1

VS bypass capacitor

Application info

100

Cvs2

4.7

μF

1. For further load/line transient details, please refer to AN5163.

Table 9. VDD1 regulator parameters (continued)

Symbol

Parameter

Test condition

Min.

Typ.

Max.

Unit

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