Renesas ISL8112EVAL1Z User Manual

USER’S MANUAL

R

12

R

11

V

OUTVFB

1–

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

=

(EQ. 1)

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 resist ors an d
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.

AN1539

Rev 0.00

February 22, 2010

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 co rrect.

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
R9 and R10 or R11 and R12 given by Equation 1:

where V

•The V
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.

= 0.7V

FB

can track OUT2REF at 1:1 ratio with input

OUT2

can also be

OUT1

FIGURE 1. TOP VIEW FIGURE 2. BOTTOM VIEW

AN1539 Rev 0.00 Page 1 of 6
February 22, 2010

ISL8112EVAL1Z

P29

P7

Q3

C17
1000PF

DNP

330UF2330UF

C30

R32

ISL8112

U1

IRF7811AV

D6

C31

P8

OPEN

MODE

P18

R15

200K

VREF2

DNP

3

4

PVCC

R12

OPEN

0.1UF

L2

VIN

C24

PH2

FS

PGOOD2

PGOOD1

EN_LDO

BYP

PVCC

PGOOD1

EN1

C7

1UF

R24

0

1000PF

6

NC

2

SW3

OPEN

BYP

VOUT1

R2

FB1

C8

FS

SW5

R16

R30

PH1

10UF

5

3

0.1UF

R18

R7

R21

R6

1

P30

1

C32

2

1

C18

R34

1

C2

C12

C13

C5

R33

2

3

1

D8

2

3

D7

1

P27

P26

5

4

3

2

1

R5

1

P24

R31

R27

R23

R19

C3

1

R17

R14

2

1

C29

2

1

R13

2

1

2

D1

1

P17

1

P12

1

P11

2

1

C11

1

2

D5

1

2

D4

R4

R3

654

3

2

1

654

3

1

654

3

2

1

SW1

654

3

2

1

SW2

R22

R20

R8

R1

1

3

D3

3

1

C27

C28

3

2

1

4

8

7

6

5

Q2

1

P1

1

P2

1

1

1

P6

1

P5

1

P4

1

P3

C26

1

432

P20

1

432

P23

R11

R10

R9

C4

C23

1

432

P21

1

432

P19

1

432

P22

C9

C10

C16

C14

C15

R25

R26

2

1

4

8

7

6

5

Q4

2

8

7

6

2

1

4

8

7

6

5

Q1

L1

OPEN

VIN

VIN

OPEN

OPEN

OPEN

0

VCC

LDO

200K

IRF7807V

0

200K

LDO

0

0

VCC

25.5

VCC

330UF

4.7UH

EN2

IRF7807V

1000PF

0.1UF

0

0

OPEN

1UF

1

VCCIN

10UF

330UF

0.1UF

200K

VOUT1

VOUT2

4.7UF

OPEN

OPEN

OPEN

OPEN

0.1UF

0

200K

0.1UF

OPEN

VOUT2

BAT54S

39.2K

SW4

3

IRF7811AV

DNP

DNP

VOUT2

PVCC

1

1

EN2

C6

VCC

EN_LDO

1

OPEN

C19

1

VREF2

VREF1

MODE

PGOOD2

NC

VREF1

P15

1

EN1

P16

VIN

3

VCC

OPEN

0.1UF

1

0.1UF

LDO

P14

0.01UF

0.1UF

1

1

D9

1

C1

D2

1UF

0.1UF

PVCC

VOUT1

BAT54S

VOUT1

P28

BYP

ILIM2

EN_LDO

FB1

GND

BOOT1

EN1

VCC

BOOT2

PVCC

PGND

NC

LG1

PH1

UG1

ILIM1

PGOOD1

EP

VSEN1

LDOREF

LDO

VIN

LG2

FS

VREF1

OUT2REF

VSEN2

MODE

PGOOD2

UG2

PH2

VREF2

EN2

3.3V

5V

ISL8112EVAL1Z Board Schematic

FIGURE 3. ISL8112EVAL1Z REV A BOARD SCHEMATIC

SW1 EN2 V

1 Connect to GND. V

NOTE: Only toggle one position at a time.

SW2 MODE OPERATING MODE

NOTE: Only toggle one position at a time.

AN1539 Rev 0.00 Page 2 of 6
February 22, 2010

2 Connect to VCC. V
3 Connect to VREF1. V

1 Connect to GND. Normal operation mode, allow automatic PWM/PFM switchover for

2 Connect to VCC. Low noise, fixed-frequency PWM mode.
3 Connect to VREF1. Ultrasonic pulse-skipping mode (20kHz min.)

TABLE 1.

output shutdown.

OUT2

TABLE 2.

output active.

OUT2

sequence to V

OUT2

pulse-skipping at light load.

OUTPUT CONTROL

OUT2

OUT1

output.