BA3259HFP Просмотр технического описания (PDF) - ROHM Semiconductor

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BA3259HFP

Dual-Output (Fixed/Variable) LDO Regulators

ROHM Semiconductor 

BA3259HFP BA30E00WHFP

Application Information

●Setting the Output Voltage Vo2

The following output voltage setting method applies to the variable output pin.

Vo2=VADJ × ( 1 +

R2

R1

) - R2 × IADJ

VADJ: Output feedback reference voltage

(0.8 V typ.)

IADJ: ADJ pin source current

(0.05µA typ.: BA3259HFP)

(0.2µA typ.: BA30E00WHFP)

Vo2

ADJ

IADJ

R2

VADJ

R1

R1

BA3259HFP: 1 kΩ to 10 kΩ

BA30E00HFP: 1 kΩ to 5 kΩ

The above is recommended.

Datasheet

Note:Connect R1 and R2 to make output voltage settings as shown in Fig.1and Fig.2. Keep in mind that the offset

voltage caused by the current (IADJ) flowing out of the ADJ pin will become high if higher resistance is used.

●Function Explanation

1) Two-input power supply (BA30E00WHFP)

The input voltages (Vcc1 and Vcc2) supply power to two outputs (Vo1 and Vo2, respectively). The power dissipation

between the input and output pins can be suppressed for each output according to usage.

Efficiency comparison:

5V single input vs. 5V/3V two inputs

•Regulator with single input and two outputs

•Regulator with two inputs and two outputs

(Vo2=1.8V, Io1=Io2=0.3A)

Conventional

Vcc

5V

Vo1

REG1

Vo2

REG2

3.3 V/0.3 A

1.8 V/0.3 A

Power loss between input and output

(Vcc − Vo1) × Io1 + (Vcc − Vo2) × Io2

= (5 − 3.3) × 0.3 + (5 − 1.8) × 0.3

= 0.51W + 0.96W

= 1.47W

→ Single 5V input results in decreased

efficiency

Current

Vcc

5V

3V

Vo1

REG1

Vo2

REG2

3.3 V/0.3 A

1.8 V/0.3 A

Power loss between input and output

(Vcc1 − Vo1) × Io1 + (Vcc2 − Vo2) × Io2

= (5 − 3.3) × 0.3 + (5 − 1.8) × 0.3

= 0.51W + 0.36W

= 0.87W

Reduced power loss by

0.6W.

→ Additional 3V input improves efficiency

2) Standby function (BA30E00WHFP)

The standby function is operated through the EN pin. Output is turned on at 2.0 V or higher and turned off at 0.8 V or

lower.

●Power Dissipation

If the IC is used under the conditions of excess of the power dissipation, the chip temperature will rise, which will have an

adverse effect on the electrical characteristics of the IC, such as a reduction in current capability. Furthermore, if the

temperature exceeds Tjmax, element deterioration or damage may occur. Implement proper thermal designs to ensure that

the power dissipation is within the permissible range in order to prevent instantaneous IC damage resulting from heat and

maintain the reliability of the IC for long-term operation. Refer to the power derating characteristics curves in Fig.27.

・Power Consumption Pc (W) Calculation Method:

○BA3259HFP

IP

Vcc

Controller

Icc

GND

Vcc

Power

Tr

Vcc

Power

Tr

• Power consumption of 3.3 V power

transistor

Pc1=(Vcc − 3.3) × Io1

• Power consumption of Vo2 power

3.3 V

Vo1 output

Io1

transistor

Pc2=(Vcc − Vo2) × Io2

• Power consumption by circuit current

Pc3=Vcc × Icc

0.8 V to

3.3 V

¶

Pc=Pc1 + Pc2 + Pc3

Vo2 output * Vcc: Applied voltage

Io2

Io1: Load current on Vo1 side

Io2: Load current on Vo2 side

Icc: Circuit current

○BA30E00WHFP

Vcc1

IB1

Controller

Vcc2

IB2

Icc1+Icc2

GND

Vcc1

Power

Tr

Vcc2

Power

Tr

• Power consumption of power transistor on

Vo1 (3.3 V output)

Pc1=(Vcc1 − Vo1) × Io1

• Power consumption of power transistor on

3.3 V

output

Io1

Io1

Vo2 (variable output )

Pc2=(Vcc2 − Vo2) × Io2

• Power consumption by circuit current

Pc3=Vcc1 × Icc1 + Vcc2 × Icc2

0.8 V to

3.3 V

¶

Pc=Pc1 + Pc2 + Pc3

Io2 output * Vcc1, Vcc2: Applied voltage

Io2

Io1: Load current on 3.3 V output side

Io2: Load current on variable output side

Icc1, Icc2: Circuit currents

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TSZ22111･15･001

11/16

TSZ02201-0R6R0A600100-1-2

26.Jun.2012 Rev.001

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