AP6714 datasheet(13/15 Pages) DIODES

13 / 15 page

AP6714

1.8MHz SYNCHRONOUS BOOST CONVERTER

AP6714 Rev. 4

13 of 15

FEBRUARY 2009

www.diodes.com

Inductor Selection

The high frequency operation of the AP6714 allows the use of small surface mount inductors. The minimum

inductance value is limited by the following constraints:

MAX

OUT

Ripple

MIN

MAX

OUT

MIN

)

(

)

(

)

(

)

(

)

(

)

(

−

Where

f= Operating frequency (Hz)

ISW(Ripple)= Allowable Inductor Current Ripple (A)

VIN(MIN)= Minimum Input Voltage (V)

VOUT(MAX)= Maximum Output Voltage (V)

Over Current Protection (OCP)

A resistor is required to connect PGND pin and OCP pin to prevent an overload occurs at the output. The

output voltage will drop and duty cycle will be reduced if the OCP exceeds 0.16V. When ROCP is 0.1Ω, the

maximum switching current to operate normally is 1.6A (0.16V/0.1

Ω). However, the actual switching current is

related to duty ratio. By the way, larger ROCP is recommended when VOUT − VIN ≤ 0.5V since the dropped output

voltage is smaller then regular case while an overload condition exists.

Internal circuit of OCP function

Thermal Information

The maximum recommended junction temperature (TJ) of AP6714 is 125°C. The thermal resistance of the

10-pin MSOP10 package is RθJA = 161°C/W, if the Power PAD is soldered. Specified regulator operation is

assured to an ambient temperature TA of 45°C. Therefore, the maximum power dissipation is about 500mW.

More power can be dissipated if the maximum ambient temperature of the application is lower.

MAX

−

)

(

)

(

Designing a PC Board

Good PC board layout is important to achieve optimal performance from AP6714. Poor design can cause

excessive conducted and/or radiated noise. Conductors carrying discontinuous currents and any high-current

path should be made as short and wide as possible. A separate low-noise ground plane contain-ing the

reference and signal grounds should connect to the power-ground plane at only one point to minimize the

effects of power-ground currents. Typically, the ground planes are best joined right at the IC. Keep the

voltage-feedback network very close to the IC, preferably within 0.2in (5mm) of the FB pin. Nodes with high

dV/dt (switching nodes) should be kept as small as possible and should be routed away from high-impedance

nodes such as FB.

Application Information

(Continued)

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