A6850KLTR-T 查看數據表（PDF） - Allegro MicroSystems

零件编号

产品描述 (功能)

生产厂家

A6850KLTR-T

Dual Channel Switch Interface IC

Allegro MicroSystems 

A6850

Dual Channel Switch Interface IC

Functional Description

Thermal Shutdown (TSD)

The A6850 protects itself from excessive heat damage by

disabling both outputs when the junction temperature, TJ ,

rises above the TSD threshold (TTSD). The outputs will

remain off until the junction temperature falls below the

TTSD level minus the TSD hysteresis, TTSDhys.

TJ can be estimated by calculating the power dissipation (PD)

of the A6850. To calculate PD:

PD = VIN IINQ

(1)

– VOUTPUT1 IOUTPUT1 – VOUTPUT2 IOUTPUT2

– VSENSE1 ISENSE1 – VSENSE2 ISENSE2 .

PD = VIN IINQ

(2)

+ (VIN – VOUTPUT1 ) IOUTPUT1

+ (VIN – VOUTPUT2 ) IOUTPUT2

+ (VIN – VSENSE1 ) ISENSE1

+ (VIN – VSENSE2 ) ISENSE2 .

The temperature rise of the A6850 can be calculated by

multiplying PD and the thermal resistance from junction to

ambient, RθJA . The formula for temperature rise, ΔT, is:

ΔT = PD × RθJA .

(3)

The RθJA for an 8-pin SOIC (Allegro L package) on a one-

layer board with minimum copper area is 140°C / W. (More

thermal data is available on the Allegro MicroSystems Web

site.)

The total junction temperature can be calculated by:

TJ = TA + ΔT ,

(4)

where TA is the ambient air temperature.

Example: Calculating the power dissipation and temperature

rise, given:

TA = 25°C,

VIN = 5 V,

IINQ = 5 mA,

IOUTPUT1 = IOUTPUT2 = 15 mA,

VDropx = VIN – VOUTPUTx = 0.7 V,

ISENSEx = IOUTPUTx /10 = 1.5 mA, and

RSENSE1 = RSENSE2 = 2 kΩ.

Then:

PD = 5 V × 5 mA

+ 0.7 V×15 mA+[5 V – (1.5 mA×2 kΩ)]×1.5 mA

+ 0.7 V×15 mA+[5 V – (1.5 mA×2 kΩ)]×1.5 mA

= 52 mW .

Substituting in equation 3:

ΔT = 52 mW × 140°C / W = 7.3°C .

Substituting in equation 4:

TJ = 25°C + 7.3°C = 32.3°C .

Output Current Limit

The A6850 limits the output current to a maximum current

of IOUTPUTM. The output current will remain at the current

limit until the output load is reduced or the A6850 goes into

thermal shutdown.

The high output current limit allows the bypass capacitor,

CBYP , on the Hall sensor to charge up quickly. This allows

a high slew rate on the VCC pin of the Hall sensor, ensur-

ing that the sensor Power-On State will be correct. See the

Applications Information section for schematic diagrams and

power calculations.

Allegro MicroSystems, Inc.



115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

Share Link: