AS1360-33-T Ver la hoja de datos (PDF) - austriamicrosystems AG

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AS1360-33-T

1.5µA Low-Power, Positive Voltage Regulator

austriamicrosystems AG 

AS1360

Datasheet - Application Information

9 Application Information

Figure 14. AS1360 - Typical Application Diagram

+9V

Alkaline

Battery

CIN

1µF *

* Tantalum Capacitor

3

2

AS1360

VIN

VOUT

GND 1

COUT

1µF *

VOUT = 3.3V

Power Dissipation

Power dissipation (PD) of the AS1360 is the sum of the power dissipated by the p-channel MOSFET and the quiescent

current required to bias the internal voltage reference and the internal power amplifier, and is calculated as:

PD (P-Channel MOSFET) = (VIN - VOUT)IOUT

(EQ 1)

Internal power dissipation as a result of the bias current for the internal voltage reference and the error amplifier is cal-

culated as:

PD (Bias) = VINIGND

(EQ 2)

Total AS1360 power dissipation is calculated as:

PD(Total) = PD (P-Channel MOSFET) + PD (Bias)

(EQ 3)

The internal quiescent bias current (2µA, typ) is such that the PD(Bias) term of (EQ 3) can be disregarded and the

maximum power dissipation can be estimated using VIN(MAX) and VOUT(MIN) to obtain a maximum voltage differential

between VIN and VOUT, and multiplying the maximum voltage differential by the maximum output current:

PD = (VIN(MAX)VOUT(MIN))IOUT(MAX)

(EQ 4)

Where:

VIN = 3.3 to 4.1V

VOUT = 3.0V ±2%

IOUT = 1 to 100mA

TAMB(MAX) = 55ºC

PMAX = (4.1V - (3.0V x 0.98)) x 100mA = 116.0mW

Junction Temperature

The AS1360 junction temperature (TJ) can be determined by first calculating the thermal resistance from junction tem-

perature-to-ambient temperature.

Note: Thermal resistance is estimated to be the junction temperature-to-air temperature RΦJA, and is approximately

230°C/W or 335ºC/W (when mounted on 1 square inch of copper). RΦJA will vary depending on PCB layout,

air-flow and application specific conditions.

The AS1360 junction temperature is determined by calculating the rise in TJ above TAMB, and then adding the increase

of TAMB:

TJ = PD(MAX) x RΦJA + TAMB

(EQ 5)

From (EQ 5), the value of TJ can be calculated as:

TJ = 116.0mW x 230ºC/W + 55ºC

Therefore:

TJ = 81.68ºC

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