ISL6310EVAL1Z Intersil, ISL6310EVAL1Z Datasheet - Page 7

• Manufacturer Part Number: ISL6310EVAL1Z
• Description: EVALUATION BOARD FOR ISL6310
• Manufacturer: Intersil

Specifications of ISL6310EVAL1Z

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.5V
• Current - Output: 60A
• Voltage - Input: 5 ~ 12V
• Regulator Topology: Buck
• Frequency - Switching: 400kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6310
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

Pre-POR Overvoltage Protection
Prior to PVCC and VCC exceeding their POR levels, the
ISL6310 is designed to protect the load from any overvoltage
events that may occur (such an overvoltage may occur if for
example one of the upper MOSFETs was shorted at
assembly due to manufacturing defects). This is
accomplished by means of an internal 10kΩ resistor tied
from PHASE to LGATE, which turns on the lower MOSFET
to control the output voltage until the input power supply
current limits itself and cuts off. In Figure 12, an artificial per-
POR overvoltage event has been created by shorting the
positive 12V input plane to the PHASE plane. This same
12V input is connected to PVCC pins of the ISL6310.
Figure 12 illustrates how the controller protects the load from
a high output voltage spike, when the 12V input turns on, by
tying LGATE to PHASE.
GND>
GND>
GND>
GND>
>
GND>
GND>
GND>
GND>
FIGURE 12. ISL6310EVAL1Z PRE-POR OUTPUT
FIGURE 11. ISL6310EVAL1Z OVERCURRENT PROTECTION
T1
OVERVOLTAGE PROTECTION (START-UP WITH
SHORTED UPPER FET)
T0
UGATE2
PGOOD
COMP
1ms/DIV
2ms/DIV
T1
7
VIN = PVCC
T2
V
OUT
T2
LGATE2
V
OUT
Application Note 1197
Overvoltage Protection
To protect from an overvoltage event during normal
operation, the ISL6310 continually monitors the output
voltage. If the output voltage exceeds a specific limit (set
internally), the controller commands the LGATE signals high,
turning on the lower MOSFETs to keep the output voltage
below a level that might cause damage to the Load. As
shown in the overvoltage event in Figure 12, turning on the
lower MOSFETs not only keeps the output voltage from
rising, it also sinks a large amount of current, causing the
input voltage to the power stage to drop. If this causes the
input power supply voltage to fall below the POR level of the
ISL6310, as seen at the end of the waveform in Figure 13,
the controller responds by using the pre-POR overvoltage
protection explained in the previous section. This allows the
ISL6310 to always keep the output load safe from high
voltage spikes during an entire overvoltage event.
Efficiency
The efficiency of the ISL6310EVAL1Z board, loaded from 0A
to 60A, at both PVCC = 5V and 12V are plotted in Figure 14
for V
temperature and taken at thermal equilibrium without any air
flow. The efficiency peaks just below 88% at 35A for the
PVCC = 12V case and then levels off steadily to
approximately 86% at 60A, while for the PVCC = 5V,
efficiency peaks at around 89% at 17A and then falls down
to approximately 84% at 60A.
GND>
GND>
GND>
FIGURE 13. ISL6310EVAL1Z PRE-POR OVERVOLTAGE
OUT
= 1.5V. Measurements were performed at room
PROTECTION
VIN = PVCC
1ms/DIV
V
OUT
LGATE2
December 12, 2006
AN1197.1