EL7516 datasheet(11/12 Pages) RENESAS

11 / 12 page

EL7516

FN7333 Rev 6.00

Page 11 of 12

October 9, 2007

where:

IL = MOSFET current limit

IL-AVG = average inductor current

IL = inductor ripple current

VDIODE = Schottky diode forward voltage, typically, 0.6V

fS = switching frequency, 600kHz or 1.2MHz

D = MOSFET turn-on ratio:

Table 1 gives typical maximum IOUT values for 1.2MHz

switching frequency and 22µH inductor:

Thermal Performance

The EL7516 uses a fused-lead package, which has a

reduced

JA of 100°C/W on a four-layer board and 115°C/W

on a two-layer board. Maximizing copper around the ground

pins will improve the thermal performance.

This device also has internal thermal shut-down set at

around +130°C to protect the component.

Layout Considerations

To achieve highest efficiency, best regulation and the most

stable operation, a good printed circuit board layout is

essential. It is strongly recommended that the demoboard

layout be followed as closely as possible. Use the following

general guidelines when laying out the print circuit board:

1. Place C4 as close to the VDD pin as possible. C4 is the

supply bypass capacitor of the device.

2. Keep the C1 ground, GND pin and C2 ground as close as

possible.

3. Keep the two high current paths a) from C1 through L1, to

the LX pin and GND and b) from C1 through L1, D1, and

C2 as short as possible.

4. High current traces should be as short and as wide as

possible.

5. Place the feedback resistor close to the FB pin to avoid

noise pickup.

6. Place the compensation network close to the COMP pin.

The demo board is a good example of layout based on these

principles; it is available upon request.

Differences Between EL7516 and ISL97516

ISL97516 is the replacement for EL7516, and it is pin-to-pin

compatible to EL7516, but there are differences between the

two parts, as shown in the Table 2:

From Table 2, it shows that ISL97516 can provide more

output current at the same conditions, and work in higher

ambient temperature. The fixed logic level also helps reduce

the system design complexity.

TABLE 1.

VIN (V)

VOUT (V)

IOMAX (mA)

2.5

570

2.5

325

2.5

250

3.3

750

3.3

435

3.3

330

650

490

I

VIN

VO VDIODE

 V

–





LVO



VDIODE fS



------------------------------------------------------------------------------

(EQ. 8)

IL-AVG

IOUT

–

-------------

(EQ. 9)

VIN

VOUT VDIODE

--------------------------------------------

–

(EQ. 10)

TABLE 2. DIFFERENCES BETWEEN EL7516 AND ISL97516

ISL97516

EL7516

Current Limit

2.0A (typical value)

1.5A (typical value)

Over-Temperature

Protection

+150°C

+130°C

Logic High or Low Level Refer to Ground,

Fixed.

Refer to input

voltage, Varying

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