2
The ISL6560 has a DAC scaled for VRM9.0 codes while the
ISL6562’s DAC is set to VRM8.5 codes. The other major
difference is the Current Comparator threshold voltage.
The typical threshold voltage for the ISL6560 is 157mV while
the ISL6562 is more sensitive and has a threshold voltage of
79mV.
Figure 3 shows the Current Comparator threshold voltage
versus the COMP voltage.
Oscillator
An oscillator drives a divider that reduces the channel
frequency to one half of the oscillator. Each channel is
initiated by the oscillator and terminated by the current
comparator. A maximum duty cycle of 50% is established by
this arrangement.
Power Good
Operation of the controller is monitored by the Power Good
circuitry which controls an open drain N-Channel MOS
transistor. When the CORE voltage is outside the 82% and
124% limits, the MOSFET pulls down an external load. Over
voltage switches both upper PWM power MOSFETs OFF
and pulls down the lower output power MOSFETs to protect
the load.
Over Current
Over current is detected by the output voltage dropping
below the under voltage limit. This results in several
occurrences. First the Current Comparator limit is reduce to
95mV from 157mV for the ISL6560 and 47mV from 79mV for
the ISL6562. This effectively folds back the current, while the
CORE voltage is now set to a lower limit of 400mV to 500mV.
Moreover, the oscillator frequency is reduce to about one
fifth of its normal operating value by reducing the oscillator
charging current to 36
µ
A from its normal operating value of
150
µ
A.
Converter Disable
To disable the converter, the COMP terminal may be pulled
to ground with a NPN transistor, N-Channel MOS transistor
or a switch. This device should be located next the COMP
pin to reduce the possibility of external pickup by the pin.
The oscillator is disabled when the COMP voltage drops
below 0.56V for the ISL6560 and 0.64V for the ISL6562.
Minimum current for the pull down device should be 2mA.
The COMP terminal is brought out as a test point on the
Evaluation Board. A ground terminal and the 3V Reference
terminal are located near the COMP terminal on the
Evaluation Board.
ISL6562 On The Board
As explained earlier the board is designed to be used with
either the ISL6560 or the ISL6562. The boards are usually
shipped with the ISL6560. Boards populated with the
ISL6562 have an additional 5m
Ω
resistor placed in the R15
location.
Evaluation Board Quick Start
To aid in getting the board functioning as quickly as possible,
a sheet similar to Figure 4 is included with each board. This
shows the location of all pertinent parts and test points.
0
20
40
60
80
100
120
140
160
0.5
1.0
1.5
2.0
2.5
3.0
0
V
CS(CL)
(mV)
V
COMP (V
olts)
n
i
= 12.5V / V
FIGURE 3. CURRENT COMPARATOR THRESHOLD
n
i
= 25V / V
ISL6562
ISL6560
VOLTAGE AS A FUNCTION OF V
COMP
ATX Connector
ATX Power Switch
VID Codes
Pin 1
12V Input for
Controller
Gate Drivers
and Load
Generator
1
5
Note: ATX Supply connected
to use ATX 5V supply for
Main Input. ATX 12V is used
for low power circuitry on board.
Main Supply Input
3.3V or 12V
Scope Probe
10mV/A
Internal
2 Position Switch
Each Position
20A at 1.500V
Current for
Load Generator
ON - OFF
each Position:
of ISL6560/62
FIGURE 4. PERTIENT POINTS ON ISL6560/62
EVALUATION BOARD
Output to an External Load
C
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ISL6560/62 Evaluation Board
