Application Note 1946
6
AN1946.0
July 7, 2014
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1.2. Functional Confirmation and Measurement
• Normal Operation with DE Mode operation at light
load.
- Set the VIN Power Supply to the desired input
voltage, then turn on electric load and set the load
current at desired value.
- Confirm the Evaluation Board output voltage,
output current, input current, efficiency, operation
mode etc.
• Overcurrent Protection.
- Set the VIN Power Supply to the desired input
voltage and sweep the load current from 0A.
- Confirm that at the OC1 level, On-duty becomes
shorter and VOUT starts to drop. Continue to
increase the current and confirm the device
triggered into Hiccup operation.
2. DE Mode Enabled/Hiccup Mode Enabled/ACL Enabled
• Short a jumper between HIC/LATCH and VCC at J13 to set
to Hiccup Mode.
• Remove a jumper between IMON/DE and GND at J8 to
enable the Average Current Limit.
• Keep jumper between IMON/DE and VCC at J11 open to
operate in DE Mode.
• Enable the system as in 1.1.
• Confirm the Input voltage, Output voltage, Load current,
operation mode and ACL functionality etc. When IMON/DE
pin voltage reaches 1.6V, ACL will be triggered. While in
ACL, On-duty becomes shorter and output voltage drops to
keep the output current at the same level.
• Turn off the VIN power supply.
3. Forced PWM Mode Enabled/Latch-off Mode Enabled/ACL
Disabled
• Short a jumper between HIC/LATCH and GND at J13 to set
to latch-off mode.
• Remove a jumper between IMON/DE and GND at J8.
• Short a jumper between IMON/DE and VCC at J11 to
operate in forced PWM mode. In forced PWM mode, the
device always operates in full synchronous mode. In light
load condition, the negative current from V
OUT
to V
IN
will
be observed.
• Enable the system as in 1.1.
• Confirm the Input voltage, output voltage, load current,
operation mode and OC2 functionality etc. When Latch-off
is triggered, the device stops switching and keeps
switching off until the EN or VIN is toggled.
• Turn off the VIN power supply.
4. For more combinations of mode settings, please refer to
Table 2
.
TABLE 2. ISL78268EV1Z MODE SETTING EXAMPLE
CONNECTOR/
TERMINAL
SIGNAL NAME
SETTING EXAMPLE
INTERNAL CLOCK/
HICCUP/
DE MODE/
ACL ENABLED
(DEFAULT SETTING)
INTERNAL CLOCK/
HICCUP/
DE MODE/
ACL DISABLED
INTERNAL CLOCK/
LATCH-OFF/
FORCED PWM/
ACL DISABLED
SYNC WITH EXT
CLOCK/ HICCUP/
FORCED PWM/
ACL DISABLED
SYNC WITH EXT
CLOCK/
LATCH-OFF/
DE MODE/
ACL ENABLED
J1
VIN
VIN +
VIN +
VIN +
VIN +
VIN +
J2
GND
VIN - (GND)
VIN - (GND)
VIN - (GND)
VIN - (GND)
VIN - (GND)
J3
PGOOD - GND -
GND - HIC/LATCH
Open Open Open Open Open
J4
VIN
-
GND
Open Open Open Open Open
J5
FB
-
GND
Open Open Open Open Open
J6
SS
-
GND
Open Open Open Open Open
J7
COMP
-GND
Open Open Open Open Open
J8
IMON/DE - GND
Open
(J11 Open = ACL
Enabled and DE
mode selected)
Short to GND
(J11 Open = DE mode
selected)
Open (J11 Short to
VCC = ACL Disabled
and Forced PWM
mode selected)
Open (J11 Short to
VCC = ACL Disabled
and Forced PWM
mode selected)
Open (J11 Open =
ACL Enabled and DE
mode selected)
J9
ISEN1P
-
GND
Open Open Open Open Open
J10
EN
Connect to Ext. EN
signal for external
On/Off control.
Or, short J28 to VCC
and short J10 Pin 2-3
for self start-up when
VIN applied.
Connect to Ext. EN
signal for external
On/Off control.
Or, short J28 to VCC
and short J10 Pin 2-3
for self start-up when
VIN applied.
Connect to Ext. EN
signal for external
On/Off control.
Or, short J28 to VCC
and short J10 Pin 2-3
for self start-up when
VIN applied.
Connect to Ext. EN
signal for external
On/Off control.
Or, short J28 to VCC
and short J10 Pin 2-3
for self start-up when
VIN applied.
Connect to Ext. EN
signal for external
On/Off control.
Or, short J28 to VCC
and short J10 Pin 2-3
for self start-up when
VIN applied.
