LP3913 datasheet(43/70 Pages) TI1

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To ADC

core

Icharge

Scaler

Vbatt

Scaler

MUX_CONTROL

VBATT

ISET

ADC1

ADC2

ADC

MUX

Current range 0 / 1

Voltage range 0 / 1

Isense

Rsense

VDD

Vbatt

ADC

1:4343

Charge

control Loop

LP3913

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SNVS489I – NOVEMBER 2006 – REVISED SEPTEMBER 2013

Battery Voltage Measurement

The battery voltage scalar transforms the battery voltage ranging from 2.6V–3.5V to the reference voltage

interval: [VREFH, 2*VREFH]. A wider voltage range (2.6V–4.4V) can be selected through I

2C by setting the voltage

range bit D7 in register 0xA to 0’b1.

Battery Charge Current Measurement

The battery charge current is indirectly measured by measuring the voltage across the ISENSE resistor. A fixed

portion of the battery charge current is mirrored over the ISENSE resistor and hence:

VISENSE = K * ICHARGE

(1)

where K is a ratio between the RSENSE current and the charge current.

The battery charge current scalar transforms the voltage across the external ISENSE resistor to the [VREFH,

2*VREFH] input voltage interval of the A/D converter.

External General Purpose Sources

Two additional A/D converter sources are available on the ADC1 and ADC2 pins of the LP3913. These two

external A/D converter sources are not internally scaled and have an input voltage range of [VREFH, 2*VREFH]. The

system designer can use these two sources for general purpose applications such as resistive keyboard matrix

scanning, temperature measurements, battery load current, battery ID resistor measurement, etc.

Figure 65. ADC Analog Front End Block Diagram

The source selection and the access to the conversion results are established through the I2C linked control

registers: ADCC and ADCD as described below:

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