ISL6224EVAL1 Intersil, ISL6224EVAL1 Datasheet - Page 6

• Manufacturer Part Number: ISL6224EVAL1
• Description: EVALUATION BOARD FOR ISL6224
• Manufacturer: Intersil

Specifications of ISL6224EVAL1

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 2.5V
• Current - Output: 3A
• Voltage - Input: 4 ~ 24V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6224
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

Over Current Protection
The ISL6224 monitors the converter output current by
measuring the voltage developed across the R
lower MOSFET and feeding it into the Isense pin through a
scaling resistor. The current detection is used by the
average current mode control loop and by the over current
detection circuit. The scaling resistor is chosen such that it
will flow 75µA of current when the converter is delivering full
load current. It is important to understand that the current
detected by the Isense pin is the sum of the DC AMPS at the
output of the converter and the positive peak of the inductor
ripple current. On page 9 of the ISL6224 data sheet is the
formula to calculate the expected peak to peak inductor
ripple current for a particular combination of VIN, VOUT,
switching frequency, and output choke inductance. The
value of “Iomax” is the sum of one half the calculated peak to
peak inductor ripple current plus the value of the output full
load current of the converter. The value of “Iomax” is now
inserted into the Risen calculation on page 6 of the ISL6224
data sheet. The over current set point Ioc is typically set at
180% of “Iomax”. The value of Ioc and the value of Risen are
inserted into the Rocset calculation on page 6 of the
ISL6224 data sheet. The ISL6224EVAL1 evaluation board
has been adjusted for 3.0 full load amps and approximately
6.3A peak inductor current for over current protection. Figure
15 shows a typical shutdown waveform when the load is
over the limit.
FIGURE 15. OUTPUT OVERLOAD SHUT DOWN
T0
6
Vin=15 V, Fs=300kHz
Inductor Current
Phase Node
DS(ON)
Application Note 9983
of the
Efficiency
The ISL6224 evaluation was designed to use the lower
MOSFETs R
through 18 show the efficiency at various output currents
and input voltages.
98.00%
93.00%
88.00%
83.00%
78.00%
98.00%
96.00%
94.00%
92.00%
90.00%
88.00%
86.00%
84.00%
82.00%
80.00%
100%
98%
96%
94%
92%
90%
88%
86%
84%
82%
80%
78%
Vin=5.6 V
FIGURE 17. EFFICIENCY WHEN VOUT = 3.3V
FIGURE 18. EFFICIENCY WHEN VOUT = 2.5V
FIGURE 16. EFFICIENCY WHEN VOUT = 5V
0
0
0
DS(ON)
5 V
0.5
0.5
0.5
5.0 V
to increase efficiency. Figures 16
7.2 V
7.2 V
Output Current
1
Output Current
1
Output Current
7.2 V
1
1.5
10.8 V
10.8 V
1.5
1.5
10.8 V
2
2
14.4 V
2
14.4 V
14.4 V
2.5
2.5
2.5
24 V
3
24 V
24 V
3
3
3.5