9

FN6435.0

February 25, 2008

Applications Information

Input Bypass Capacitor

The input capacitor is required to suppress the power supply

transient response during transitions. Typically, a 10µF or

larger capacitor should be sufficient to suppress the power

supply noise.

Due to the inductance of the power leads of the wall adapter

or USB source, the input capacitor type must be properly

selected to prevent high voltage transient during a hot-plug

event. A tantalum capacitor is a good choice for its high

ESR, providing damping to the voltage transient. Multi-layer

ceramic capacitors, however, have a very low ESR and

hence when chosen as input capacitor, a 1

Ω series resistor

must be used (as shown in the “Typical Application Circuit”

on page 6) to provide adequate damping.

VOUT and VBAT Capacitor Selection

The criteria for selecting the capacitor at the VOUT and

VBAT pins is to maintain the stability as well as to bypass

any transient load current. The recommended capacitance is

a 4.7µF X5R ceramic capacitor for VOUT and 1µF for VBAT.

The actual capacitance connected to the output is

dependent on the actual application requirement.

Layout Guidance

The ISL9301 uses a thermally-enhanced DFN package that

has an exposed thermal pad at the bottom side of the

package. The layout should connect as much as possible to

copper on the exposed pad. Typically, the component layer

is more effective in dissipating heat. The thermal impedance

can be further reduced by using other layers of copper

connecting to the exposed pad through a thermal via array.

Each thermal via is recommended to have 0.3mm diameter

and 1mm distance from other thermal vias.

Input Power Sources

The input power source is typically a well-regulated wall

cube with 1m length wire or a USB port. The input voltage

ranges from 4.3V to 10V. The ISL9301 can withstand up to

28V on the input without damaging the IC. If the input

voltage is higher than the OVP threshold, the IC is disabled.

State Diagram

The state diagram is shown in Figure 6. There are 8 states to

cover all the operation modes, including the Trickle Charge,

Batt Discharge, PPM, CV Charge, Charge Fault, Charge

Complete, Disabled and OTP states.

The IC starts with a trickle charge or constant current charge

state depending on VBAT when input power is applied. In

the Trickle Charge state, the PPR is LO and the CHG is LO,

VOUT

X3

X3

VIN

TEMPERATURE

MONITORING

X3

VBAT

+

-

VREF

VA

+

-

CA

IREF

CONTROL

IREF

REF

Q1

Q2

FIGURE 4. CHARGE CURRENT THERMAL FOLDBACK CIRCUIT

TEMPERATURE

115°C

ISEN

-40mA/°C

FIGURE 5. CHARGE CURRENT FOLDBACK

ISL9301