LTC4100_09 datasheet(24/30 Pages) LINER

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LTC4100

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b) ITHRM current is due to SafetySignal (thermistor pin)

sampling that will vary with the presence of DC power

being on or off. DCDIV is detected every 32ms. RTHX

is the value of the safety signal resistance, which will

vary with temperature or battery conﬁguration.

b1)ITHRM(ON) when DC is on:

ITHRM(ON)_OVERRANGE = 1/16 • VDD/(54.9k + RTHX)

where RTHX > 100k

ITHRM(ON)_COLD = 1/8 • VDD/(54.9k + RTHX) where

RTHX > 30k

ITHRM(ON)_NORMAL = 1/8 • VDD/(54.9k + RTHX)

+ 1/16 • VDD/(1.13k + RTHX)

ITHRM(ON)_HOT* = 1/8 • VDD/(54.9k + RTHX)

+ 1/8 • VDD/(1.13k + RTHX)

where RTHX < 3k

*= includes underrange

b2)ITHRM(OFF) when DC is off, the thermistor monitoring

rate is reduced to every 250ms or less.

ITHRM(OFF)_OVERRANGE = 1/50 • VDD/(54.9k + RTHX)

where RTHX > 100K

ITHRM(OFF)_COLD = 1/50 • VDD/(54.9k + RTHX)

+ 1/1000 • VDD/(54.9k + RTHX)

where RTHX > 30K

ITHRM(OFF)_NORMAL = 1/50 • VDD/(54.9k + RTHX) +

1/500 • VDD/(54.9k + RTHX) + 1/1000 • VDD/(1.13k

+ RTHX)

ITHRM(OFF)_HOT* = 1/50 • VDD/(54.9k + RTHX) +

1/500 • VDD/(54.9k + RTHX) + 1/500 • VDD/(1.13k +

RTHX)

where RTHX < 3k

* includes underrange

APPLICATIONS INFORMATION

c) IACCEL is the current used by the SMBus accelerators.

This directly depends on the SMBus frequency, duty

cycle of messages sent on the SMBus and how long

it takes to drive the SMBus to VDD.

IACCEL = IPULL-UP • 2 • SMBus Frequency •

Message Duty Cycle •VDD/2.25V• Rise Time

Complete Examples

1) Battery thermistor = 400Ω, VDD = 5.0V

Battery mode (DC is off), SMBus activity is 10kHz

and a 2% SMBus duty cycle, which represents a

suspended or sleep condition of a notebook.

ITOTAL= IRUN + ITHRM(OFF) + IACCEL = 121.9μA

+ 5.26μA + 2.44μA = 130μA

Battery mode and a 10% SMBus duty cycle, which

represents an active notebook at idle.

ITOTAL= IRUN + ITHRM(OFF) + IACCEL = 189.5μA

+ 5.26μA + 12.2μA = 207μA

DCIN = ON and a 20% SMBus duty cycle which

represents an active notebook charging.

ITOTAL= IRUN + ITHRM(ON) + IACCEL = 274μA

+ 215.6μA + 24.4μA = 514μA

2) Battery thermistor = 10kΩ, VDD = 5.0V

Battery mode (DC is off), SMBus activity is 10kHz

and a 2% SMBus duty cycle:

ITOTAL= IRUN + ITHRM(OFF) + IACCEL = 121.9μA

+ 2.14μA + 2.44μA = 126μA

Battery mode and a 10% SMBus duty cycle:

ITOTAL= IRUN + ITHRM(OFF) + IACCEL = 189.5μA

+ 2.14μA + 12.2μA = 204μA

DCIN = ON and a 20% SMBus duty cycle:

ITOTAL= IRUN + ITHRM(OFF) + IACCEL = 274μA

+ 37.7μA + 24.4μA = 336μA

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