ISL8200AM INTERSIL [Intersil Corporation], ISL8200AM Datasheet - Page 16

• Manufacturer Part Number: ISL8200AM
• Description: Complete Current Share 10A DC/DC Power Module
• Manufacturer: INTERSIL [Intersil Corporation]

Power Good
The Power-Good comparators monitor the voltage on the internal
VMON1 pin. The trip points are shown in Figure 30. PGOOD will
not be asserted until after the completion of the soft-start cycle.
The PGOOD pulls low upon both EN’s disabling it or the internal
VMON1 pin’s voltage is out of the threshold window. PGOOD will
not be asserted until after the completion of the soft-start cycle.
PGOOD will not pull low until the fault is present for three
consecutive clock cycles.
The UV indication is not enabled until the end of soft-start. In a UV
event, if the output drops below -13% of the target level due to
some reason (cases when EN is not pulled low) other than OV,
OC, OT, and PLL faults, PGOOD will be pulled low.
Current Share
The IAVG_CS is the current of the module. ISHARE and ISET pins
source a copy of IAVG_CS with 15µA offset, i.e., the full scale will
be 126µA.
The share bus voltage (V
(R
active modules. The voltage (V
average current of the corresponding module and is compared
with the share bus (V
(ICSH_ER) is then fed into the current correction block to adjust
each module’s PWM pulse accordingly. The current share
function provides at least 10% overall accuracy between ICs, up
to 3 phases. The current share bus works for up to 6-phase.
Figure 4 further illustrates the current sharing aspects of the
ISL8200AM.
When there is only one module in the system, the ISET and
ISHARE pins can be shorted together and grounded via a single
resistor to ensure zero share error - a resistor value of 5k
(paralleling 10k on ISET and ISHARE) will allow operation up to
the OCP level.
ISHARE
PGOOD
VMON1
FIGURE 30. POWER-GOOD THRESHOLD WINDOW
= R
CHANNEL 1 UV/OV
ISET
/NCTRL) represents the average current of all
END OF SS1
ISHARE
ISHARE
). The current share error signal
16
ISET
) set by an external resistor
) set by R
AND
PGOOD LATCH OFF
AFTER 120% OV
ISET
represents the
PGOOD
+13%
+9%
V
-9%
-13%
+20%
REF
ISL8200AM
Overvoltage Protection (OVP)
The Overvoltage (OV) protection indication circuitry monitors the
voltage on the internal VMON1 pin.
OV protection is active from the beginning of soft-start. An OV
condition (>120%) would latch the IC off (the high-side MOSFET
to latch off permanently; the low-side MOSFET turns on
immediately at the time of OV trip and then turns off
permanently after the output voltage drops below 87%). The EN
and PGOOD are also latched low at OV event. The latch condition
can be reset only by recycling VCC.
There is another non-latch OV protection (113% of target level).
At the condition of EN low and the output over 113% OV, the
lower side MOSFET will turn on until the output drops below 87%.
This is to protect the overall power trains in case of a single
channel of a multi-module system detecting OV. The low-side
MOSFET always turns on at the conditions of EN = LOW and the
output voltage above 113% (all EN pins are tied together) and
turns off after the output drops below 87%. Thus, in a high phase
count application (multi-module mode), all cascaded modules
can latch off simultaneously via the EN pins (EN pins are tied
together in multiphase mode), and each IC shares the same sink
current to reduce the stress and eliminate the bouncing among
phases.
Over-Temperature Protection (OTP)
When the junction temperature of the IC is greater than +150°C
(typically), EN pin will be pulled low to inform other cascaded
channels via their EN pins. All connected ENs stay low and
release after the IC’s junction temperature drops below +125°C
(typically), a +25°C hysteresis (typically).
Overcurrent Protection (OCP)
The OCP function is enabled at startup. The load current
sampling ICS1 is sensed by sampling the voltage across Q2
MOSFET r
OCSET and PHASE pin. IC1 is compared with the Channel
Overcurrent Limit ‘111µA OCP’ comparator, and waits 7-cycles
before OCP condition is declared. The module’s output current
(ICS1) plus a fixed internal 15µA offset forms a voltage (V
across the external resistor, R
precision internal 1.2V threshold for a second method to detect
OCP condition.
Multi-module operation can be achieved by connecting the
ISHARE pin of two or more modules together. In multi-module
operation the voltage on the ISHARE pin correlates to the
average current of all active channels. The output current of each
module in multi-module operation is compared to a precise 1.2V
threshold to determine the overcurrent condition. Additionally,
each module has an overcurrent trip point of 111µA with 7-cycle
delay. Note that it is not necessary for the R
to trip at the same level as the 111µA OCP comparator. Typically
the ISHARE pin average current protection level should be higher
than the phase current protection level.
With an internal R
default value. To lower the OCP level, an external R
connected between OCSET and PHASE pin. The relationships
between the external R
current I
OUT(MAX)
DS(ON)
during turn on through the resistor between
OCP levels for ISL8200AM are shown in
ISEN-IN
ISEN-EX
of 2.2kΩ, the OCP level is set to the
ISHARE
values and the typical output
. V
ISHARE
ISHARE
is compared with a
September 13, 2012
ISEN-EX
to be scaled
ISHARE
FN8271.2
is
)