Renesas ISL8112EVAL1Z User Manual

ISL8112EVAL1Z
Evaluation Board Setup Procedure
The ISL8112 is a dual-output Synchronous Buck
controller with 2A integrated driver. It features high
light load efficiency which is especially preferred in
systems concerned with high efficiency in wide load
range, like the battery powered system. ISL8112
includes two constant on-time PWM controllers. Both
outputs can operate in an output fixed mode or an
adjustable mode. In fixed mode, one output can be 5V
or 3.3V and the other 1.5V or 1.05V. In adjustable
mode, one output can range from 0.7V to 5.5V, and the
other from 0V to 2.5V (sensing output voltage directly)
or up to 5V (using resistor divider voltage for voltage
sensing). This device also features a linear regulator
providing 3.3V/5V, or adjustable from 0.7V to 4.5V via
LDOREF. The linear regulator provides up to 100mA
output current with automatic linear-regulator
bootstrapping to the BYP input. When in switchover, the
LDO output can source up to 200mA. ISL8112 includes
on-board power-up sequencing, the power-good
(PGOOD_) outputs, digital soft-start, and internal
soft-stop output discharge that prevents negative
voltages on shutdown.
ISL8112 is implemented with constant on-time PWM
control scheme which need no sense resistors and
provides 100ns response to load transients while
maintaining a relatively constant switching frequency.
The unique ultrasonic pulse-skipping mode maintains
the switching frequency above 25kHz, eliminating
undesired audible noises in low frequency operation at
light load. Other features include pulse skipping which
maximizes efficiency in light-load applications, and
fixed-frequency PWM mode which reduces RF
interference in sensitive applications.
FIGURE 1. TOP VIEW
AN1539 Rev 0.00
February 22, 2010
USER'S MANUAL
Recommended Equipment
• 0V to 25V power supply with at least 20A source
current capability, battery, or notebook AC adapter.
• Two electronic loads capable of sinking current up
to 15A.
• Dummy loads for the LDO's.
• Digital multimeters (DMMs).
• 100MHz quad-trace oscilloscope.
• Signal generator.
Quick Start
1. Ensure that the circuit is correctly connected to the
supply and loads prior to applying any power.
2. Verify that position 2's are ON for SW1, SW2, SW3,
SW4, and SW5. Make sure that no other position of
each switch is ON at the same time.
3. Turn on the input power supply.
4. Verify the output voltages are correct.
5. Verify the LDOs output voltages are correct.
Evaluating the Other Output Voltage
The ISL8112EVAL1Z board outputs are preset to 5V/7A,
3.3V/7A and 5V/200mA on LDO. The V
adjusted between 0.7V to 5.5V by changing the value of
R and R or R and R
9 10 11 12
R
11
R -------------------------------------------- -
=
12    1
V V –
OUT FB
where V = 0.7V
FB
• The V can track OUT2REF at 1:1 ratio with input
OUT2
voltage range from 0.7V to 2.5V. Likewise, the LDO
output can also track LDOREF at 1:2 with voltage
range from 0.35V to 2.25V.
FIGURE 2. BOTTOM VIEW
AN1539
Rev 0.00
February 22, 2010
can also be
OUT1
given by Equation 1:
(EQ. 1)
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