Renesas ISL8106EVAL1Z User Manual

ISL8106EVAL1Z
Evaluation Board
The ISL8106EVAL1Z evaluation board demonstrates the
performances of the ISL8106, synchronous buck PWM
controller with Intersil's Robust Ripple Regulator (R3)
technology.
The ISL8106 features a 1.5ms digital soft-start and can be
started into a pre-biased output voltage. The PWM switching
frequency can be programmed from 200kHz to 600kHz. The
ISL8106 can be configured to operate in
Forced-Continuous-Conduction-Mode (FCCM) or in
Diode-Emulation-Mode (DEM), which improves light-load
efficiency. An audio filter prevents the PWM switching
frequency from entering the audible spectrum due to
extremely light load while in DEM. Refer to the ISL8106 data
sheet for a more detailed operation by clicking on the
following link.
http://www.intersil.com/data/fn/fn9283.pdf
ISL8106EVAL1Z Reference Design
The ISL8106EVAL1Z design criteria is listed in Table 1.
TABLE 1. ISL8106EVAL1Z DESIGN CRITERIA
PARAMETERS
Input Voltage
Output Voltage
Rated Output Current
Switching Frequency
Setting Switching Frequency
The switching frequency of ISL8106EVAL1Z can be adjusted
through the resistor, R , that is connected from the FSET pin
5
to the GND pin. Programming the approximate PWM
switching frequency can be estimated from Equation 1:
1
------------------------------------------------------- -
R =
FSET
12
–
 10
60 F 1
 
OSC
Setting Overcurrent Protection Threshold
An overcurrent protection fault will occur when the ISEN pin
has measured more than the OCP threshold current I
(26µA, typ.), on consecutive PWM pulses, for a period
exceeding 20µs. It does not matter how many PWM pulses
are measured during the 20µs period. If a measurement falls
below I before 20µs has elapsed, then the timer is reset
OC
to zero. A short circuit protection fault will occur when the
ISEN pin has measured more than the short-circuit threshold
current I in less than 10µs, on consecutive PWM pulses.
SC,
The value of RSEN can then be calculated by Equation 2:
I
P-P
I --------- - OC r
+
 
FL SP
2
----------------------------------------------------------------------------- -
R =
SEN
I
OC
AN1452 Rev 0.00
Feb 16, 2009
VALUE
7V to 25V
1.8V
25A
300kHz
(EQ. 1)

OC
 
DS ON
(EQ. 2)
USER'S MANUAL
Where:
- R () is the resistor used to program the
SEN
overcurrent setpoint
- I is the I threshold current value sourced from the
OC SEN
ISEN pin that will activate the OCP circuit
- I is the maximum continuous DC load current
FL
- I is the inductor peak-to-peak ripple current
P-P
- OC is the desired overcurrent setpoint expressed as
SP
a multiplier relative to I
FL
Power and Load Connections
INPUT VOLTAGE
The PVIN post (J1) is connected to the drain of the upper
MOSFET and the VIN pin of the IC. The post (J2) is
connected to PGND.
OUTPUT VOLTAGE LOADING AND MONITORING
Connect the positive and negative leads of an electronic
load to J3 and J4 respectively. Terminal TP4 (PGND) and
TP5 (V ) can be used to measure the output voltage.
OUT
Switch Descriptions
TABLE 2. ISL8106EVAL1Z SWITCH DESCRIPTIONS
TOGGLE SWITCHES
SW1 OFF: Shorts the EN pin to GND (Disable
ON: Enable the controller, EN pin is pulled
to V
SW2 DEM: FCCM pin is pulled to GND to
FCCM: FCCM pin is pulled to VCC to
Test-point Descriptions
TABLE 3. ISL8106EVAL1Z TEST POINT DESCRIPTIONS
TEST POINTS
TP1
TP2
TP3
TP4
TP5
TP6
TP6
AN1452
Rev 0.00
Feb 16, 2009
FUNCTION
the controller)
and clamped by D1.
IN
enable diode-emulation mode
inhibits diode-emulation mode
SIGNALS
VCC
PGND
PGOOD
PGND
VOUT
PVIN
LX
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