MAX8515A 查看數據表（PDF） - Maxim Integrated

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MAX8515A

Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters

Maxim Integrated 

Wide-Input 0.6V Shunt Regulators for

Isolated DC-to-DC Converters

VREG

1.8V

R1

47kΩ

V+

MAX5003

NDRV

PGND

CON

INPUT

SUPPLY

C1

0.1µF

IN

OUT

MAX8515A

MAX8515

PGND

GND

FB

R3

20kΩ

1%

R4

10kΩ

1%

C2

0.1µF

R2

C4

C3

Figure 3. MAX8515A/MAX8515 Typical Application Circuit,

Opto-Feedback Circuit

6V TO 10V

R1

1.2kΩ

R2

2kΩ

C1

0.1µF

16V

IN

OUT

MAX8515A

MAX8515

PGND

GND

FB

FEEDBACK

OPTOCOUPLER

DC-DC OUTPUT

0.8V

R3

6.2kΩ

1%

R4

10kΩ

1%

Figure 4. MAX8515A/MAX8515 Typical Application Circuit,

OVP Circuit (Set to 1V OVP Threshold for 0.8V Nominal Output)

Overvoltage Protection

Figure 4 shows an isolated OVP circuit. R1 limits the

current supplied to the photodiode. R2 limits the

MAX8515A/MAX8515 input current. R3 and R4 set the

trip threshold for the OVP. C1 is the input supply

decoupling capacitor.

Values for R3 and R4 are chosen based on the needed

OVP threshold. For example, a trip threshold of 25%

above the rated output voltage is needed for an OVP

circuit. The values of R3 can be determined from the

following equation once R4 is chosen; 10kΩ is recom-

mended for R4. Then, R3 = 6.2kΩ.

R3

=







VOVP

VFB



- 1



× R4

where VOVP = 0.8V x 1.25 for the given example.

Linear Regulator

Use an external pass transistor in conjunction with the

MAX8515A/MAX8515 to create a linear regulator as

shown in Figure 5. Determine the output voltage of the

regulator by:

VREG

=

0.6V

×

1

+

R2 

R3 

Choose R1 to maintain load regulation up to a 2A load.

Use the following equation:

R1 = VIN_MIN - VREG - VBE × β

IO_MAX

where IO_MAX is the rated maximum output current,

which is 2A in this application circuit. VREG is the output

voltage of the linear regulator. VBE is the base-to-emitter

forward voltage of Q1, and β is the minimum current gain

of Q1 at rated load current. VIN is the minimum input volt-

age at IN. For the typical application circuit, VIN_MIN =

2.375V, VREG = 1.0V, VBE = 0.65V, and β = 180. Choose

R1 = 15Ω for fast transient response. C1 is the input

decoupling capacitor and C2 is the compensation

capacitor. Use a 1µF, 6.3V capacitor for this application.

Figure 6 shows a typical load-regulation curve for the cir-

cuit in Figure 5. This circuit does not provide short-circuit,

overcurrent, or overtemperature protection.

6 _______________________________________________________________________________________

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