LTC4162IUFD-FST#PBF datasheet(18/52 Pages) AD

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LTC4162-F

Rev A

For more information www.analog.com

OPERATION

System Controls

The switching battery charger can be disabled by setting

suspend_charger.Thismightbenecessary,forinstance,to

pass USB Suspend compliance testing. suspend_charger

should be used with caution as a low battery situation

could prevent the system processor from being able to

clear it and may require a factory service call to remove

and replace the battery.

Input Overvoltage Protection

The LTC4162 has over-voltage detection on its input. If

VINexceedsapproximately38.6Vasindicatedbyvin_ovlo,

the switching charger will stop delivering power. The

charger will resume switching if VIN falls below roughly

37.2V. The overvoltage detection cutoff circuit provides

only modest over voltage protection and is not intended

to prevent damage in all circumstances.

Measurement Subsystem

TheLTC4162includesa16-bitΔΣA/Dconverterandsignal

multiplexer to monitor numerous analog parameters. It

can measure the voltages at vin, vbat and vout, the input

current (voltage between CLP and CLN), iin, the battery

charge current (voltage between CSP and CSN), ibat, the

batterypackthermistor_voltage,itsowninternaldie_temp

and, once a charge cycle begins, the series resistance of

the battery, bsr. To save battery current, the measure-

ment system is disabled if the battery is the only source

of power (vin_gt_vbat = 0). This can be overridden with

force_telemetry_on. The A/D converter is automatically

multiplexed between all of the measured channels and

its 16-bit signed two's complement results are stored in

registers accessible via the I2C port. The seven channels

measured by the ADC each take approximately 1.6ms to

convert. The maximum range of the 16 bit ΔΣ A/D con-

verter is ±1.8V and it has an internal span term of 18191

counts per Volt. It measures each of the above parameters

through different paths giving different sensitivity terms

for each measurement as summarized in Table 1.

Battery Voltage Measurement

Battery voltage is measured through a resistive voltage

divider whose attenuation ratio is based on the cell_count.

The result is reported in vbat. The divider ratio is BAT-

SENS+/(3.5 • cell_count) making the A/D span term

3.5 • cell_count/18191 or 192.4µV • cell_count per LSB

where cell_count varies from 1 to 9. An alert may be

set on battery voltage by setting the vbat based value

vbat_lo_alert_limit or vbat_hi_alert_limit and setting

en_vbat_lo_alert or en_vbat_hi_alert. These alerts are

indicated by vbat_lo_alert or vbat_hi_alert and are cleared

by writing them to 0.

Input Voltage Measurement

Input voltage is measured through a 30:1 resistive volt-

age divider making the A/D span term for input voltage

measurements 30/18191 or 1.649mV/LSB and is digitized

to vin. An alert may be set on input voltage by setting the

value vin_lo_alert_limit or vin_hi_alert_limit and setting

en_vin_lo_alert or en_vin_hi_alert. These alerts are indi-

cated by vin_lo_alert and vin_hi_alert and are cleared by

writing them to 0.

Table 1. Measurement Subsystem LSB Sizes

MEASUREMENT

UNITS

LSB SIZE

OFFSET

BATTERY VOLTAGE

vbat

192.4µV • cell_count

INPUT VOLTAGE

vin

1.649mV

OUTPUT VOLTAGE

vout

1.653mV

INPUT CURRENT

iin

1.466µV/RSNSI

BATTERY CURRENT

ibat

1.466µV/RSNSB

DIE TEMPERATURE

°C

die_temp

0.0215°C

264.4°C

BATTERY IMPEDANCE

bsr

RSNSB • cell_count/500

THERMISTOR VOLTAGE

thermistor_voltage

45.833µV/V

LTC4162IUFD-FST#PBF 数据表(PDF) 18 Page - Analog Devices

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