ISL8014AEVAL2Z datasheet(14/16 Pages) RENESAS

14 / 16 page

ISL8014A

FN7525 Rev 2.00

Page 14 of 16

December 16, 2014

As an example, let VIN = 5V with rise time, T = 10ms. Then

R4 =56.2kΩ, R5 = 71.5kΩ, and C = 0.68µF are used to insure

that VIN was >2.5V and the EN voltage was <400mV.

Discharge Mode (Soft-stop)

When a transition to shutdown mode occurs or the VIN UVLO is

set, the outputs discharge to GND through an internal 100Ω

switch.

Power MOSFETs

The power MOSFETs are optimized for best efficiency. The

ON-resistance for the P-MOSFET is typically 50mΩ and the

ON-resistance for the N-MOSFET is typically 50mΩ.

100% Duty Cycle

The ISL8014A features 100% duty cycle operation to maximize

the battery life. When the battery voltage drops to a level that the

ISL8014A can no longer maintain the regulation at the output,

the regulator completely turns on the P-MOSFET. The maximum

dropout voltage under the 100% duty-cycle operation is the

product of the load current and the ON-resistance of the

P-MOSFET.

Thermal Shut-Down

The ISL8014A has built-in thermal protection. When the internal

temperature reaches +140°C, the regulator is completely shut

down. As the temperature drops to +115°C, the ISL8014A

resumes operation by stepping through the soft-start.

Applications Information

Output Inductor and Capacitor Selection

To consider steady state and transient operations, ISL8014A

typically uses a 1.5µH output inductor. The higher or lower

inductor value can be used to optimize the total converter system

performance. For example, for higher output voltage 3.3V

application, in order to decrease the inductor current ripple and

output voltage ripple, the output inductor value can be increased.

It is recommended to set the ripple inductor current

approximately 30% of the maximum output current for optimized

performance. The inductor ripple current can be expressed as

shown in Equation 3:

The inductor’s saturation current rating needs to be at least

larger than the peak current. The ISL8014A protects the typical

peak current 6A. The saturation current needs be over 7A for

maximum output current application.

ISL8014A uses internal compensation network and the output

capacitor value is dependent on the output voltage. The ceramic

capacitor is recommended to be X5R or X7R. The recommended

X5R or X7R minimum output capacitor values are shown in

Table 1.

Table 1 shows the minimum output capacitor value is given for

the different output voltage to make sure that the whole

converter system is stable. Additional output capacitance should

be added for better performances in applications where high

load transient or low output ripple is required. It is recommended

to check the system level performance along with the simulation

model.

Output Voltage Selection

The output voltage of the regulator can be programmed via an

external resistor divider that is used to scale the output voltage

relative to the internal reference voltage and feed it back to the

inverting input of the error amplifier. Refer to the “Typical

Application” on page 3.

The output voltage programming resistor, R3, will depend on the

value chosen for the feedback resistor and the desired output

voltage of the regulator. The value for the feedback resistor is

typically between 10kΩ and 100kΩ

as shown in Equation 4.

If the output voltage desired is 0.8V, then R3 is left unpopulated

and R2 is shorted. There is a leakage current from VIN to LX. It is

recommended to preload the output with 10µA minimum. For

better performance, add 47pF in parallel with R2 (100kΩ

Input Capacitor Selection

The main functions for the input capacitor are to provide

decoupling of the parasitic inductance and to provide filtering

function to prevent the switching current flowing back to the

battery rail. Two 22µF X5R or X7R ceramic capacitors are a good

starting point for the input capacitor selection.

I

VO 1

VIN

---------

–









LfS



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

(EQ. 3)

TABLE 1. OUTPUT CAPACITOR VALUE vs VOUT

VOUT

(V)

COUT

(µF)

(µH)

0.8

2 x 22

1.0~2.2

1.2

2 x 22

1.0~2.2

1.5

2 x 22

1.5~3.3

1.8

2 x 22

1.5~3.3

2.5

2 x 22

1.5~3.3

3.3

2 x 22

2.2~4.7

3.6

2 x 22

2.2~4.7

R2 0.8V



VOUT 0.8V

–

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

(EQ. 4)

ISL8014AEVAL2Z bảng dữ liệu(PDF) 14 Page - Renesas Technology Corp

ISL8014AEVAL2Z bảng dữ liệu(HTML) 14 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

bảng dữ liệu tải về

Link URL