7
FN9028.1
July 2004
enabling the accompanying voltage converter. The DC-DC
converter then provides a well regulated output voltage to
the IM circuitry.
Available from Intersil is the ISL6160EVAL2. The
ISL6160EVAL2 is a complete InfiniBand Class I (non isolated)
power topology evaluation platform consisting of the ISL6160
and the HIP6006 single output PWM controller. See Figure 2
for a simplified block diagram of the ISL6160EVAL2 platform.
This evaluation platform allows the Infiniband Module (IM)
power supply designer to evaluate the concept of this design
and apply it to a specific IM power requirement. The evaluation
platform is configured for 5V Vout and 3A Iout capability and
exhibits a 92% total efficiency. See Figures 19 and 20 for
ISL6160EVAL2 turn-on and turn-off waveforms.
Additional information for the ISL6160EVAL2 can be found in
application note AN9959.
Using the ISL6160 beyond IM Applications
-48V, +5V Control Circuit
The ISL6160 can also be used for -48V and +5V telecom
power control. The VB portion of the ISL6160 configured as a
low side switch controller as shown in Figure 3. is capable of
controlling several hundreds of volts, positive or negative and at
the same time provide control and protection for the +5V supply
with its 1A integrated current regulating function.
Biased by an external 12V reference in the low side switch
configuration the ISL6160 retains all of its features except for
the DC-DC_EN feature. This is nonfunctional in the low side
configuration as V
ISEN
is always near 0V and will not pull high
to indicate that voltage is good.
When controlling a negative voltage the VB_ON control can
be implemented through an optocoupler for on-off control or
left open for an always on hot pluggable adaptor card
application .
Application Considerations
The manufacturers’ MOSFET safe operating area (SOA) data
should be consulted, as during the soft start ramp and current
regulation times, the VGS of the external N-Channel MOSFETs
is reduced driving the N-Channel MOSFET switch into the
(linear region) high rDS(ON) state. Thus avoid extended soft
start and time out periods as the external N-Channel MOSFETs
may be damaged or destroyed due to excessive internal power
dissipation. Refer to the MOSFET manufacturers’ data sheets
for SOA information.
With the high levels of inrush current e.g., highly capacitive
loads and HDD motor start up currents, choosing the ramp up
rate and regulation level of the load current is crucial to provide
both protection and still allow for this inrush current without
latching off. Consider this in addition to the time out delay when
choosing MOSFETs for your design.
Correct physical layout of RSENSE resistor is critical to the
accuracy of sensing the VB current. Ideally trace routing
between the R
SENSE
resistors and the ISL6160 is direct and
as short as possible with zero current in the sense lines. (See
Figure 4.)
FIGURE 2. SIMPLIFIED ISL6160EVAL2 BLOCK DIAGRAM
LCL_POWER_EN
VBX_EN_L
ISL6160
HIP6006
VB CONTROL
VA CONTROL
VB_IN
VA_IN
VAout
Vout
VB_ON
DC-DC_ON
EN
HI GATE
LO_GATE
5
6
8
7
4
3
2
1
9
10
11
12
13
14
FIGURE 3. -48V/+5V APPLICATION CIRCUIT
0V
+
-
LOAD
+5V
LOAD
+
-
+5V
12V
REG
-48V
-48V
ISL6160
CORRECT
TO ISEN AND
CURRENT
SENSE RESISTOR
INCORRECT
FIGURE 4. SENSE RESISTOR PCB LAYOUT
R
ISET
ISL6160
