ACE710

0.9V startup, 0.6A 3.3V/5V Synchronous Boost DC/DC Converter

VER 1.3

6

True shut off function

ACE710 offers a true shut off function, which means it can really shut off output (make output voltage to

zero) when EN is pull low (chip turns off). Normally, there is a schottky diode (or MOSFET body diode)

existed between SW and Vout for a normal boost converter, and thus, when EN is pull low, though the

chip is turned off, the Vin is connected to Vout thru inductor and schottky diode. So we still can detect a

voltage at Vout terminal. ACE710, with its proprietary design skill, can truly shut down the output when

chip is turned off.

Design Procedure

Setting Output Voltages

Output voltages are set by external resistors. The FB_ threshold is 0.6V.

RTOP = RBOTTOM[(VOUT / 0.6) - 1]

Capacitor Selection

A 22uF ceramic capacitor is demanded on output terminal, while 4.7uF is good enough for input.

Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their

high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications.

Using ceramic capacitors can achieve very low output ripple and small circuit size. When choosing the

input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics

have the best temperature and voltage characteristics of all the ceramics for a given value and size.

Application Information

Layout is critical to achieve clean and stable operation. The switching power stage requires particular

attention. Follow these guidelines for good PC board layout:

1. Place 22uF output capacitors as close to the IC VOUT and GND pins as possible

2. Connect input and output capacitors to the same power ground node with a star ground configuration

then to IC ground.

3. Keep the high-current paths as short and wide as possible. Keep the path of switching current short.

Avoid vias in the switching paths.

4. If possible, connect VIN, SW, and GND separately to a large copper area to help cool the IC to further

improve efficiency and long-term reliability.

5. Ensure all feedback connections are short and direct. Place the feedback resistors as close to the IC

as possible.

6. Route high-speed switching nodes away from sensitive analog areas