ISL8120IRZ Intersil, ISL8120IRZ Datasheet - Page 29

• Manufacturer Part Number: ISL8120IRZ
• Description: IC CTRLR PWM 2PHASE W/DVR 32-QFN
• Manufacturer: Intersil

Specifications of ISL8120IRZ

• Pwm Type: Voltage Mode
• Number Of Outputs: 2
• Frequency - Max: 1.5MHz
• Duty Cycle: 90%
• Voltage - Supply: 3 V ~ 22 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Frequency-max: 1.5MHz
• Rohs Compliant: YES
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The second option for multi-module parallel system is to
have only one signal (ISHARE) wire connection. The signal
wire connection scheme is targeted for a N+1 system, where
each module is a standard one that can be paralleled to build
up power systems with different capacity, and each module
can start-up at different time, and each module can be shut
down and removed without the system shutdown. Figure 15
shows some extra circuits needed for such a parallel module
system (each module with independant voltage feedback
loop where only one analog signal (ISHARE) wire is
connected between the module) besides the circuits shown
in “Typical Application VIIII (4 Outputs Operation with DCR
Sensing)” on page 13. The circuitry shown in Figure 15 is to
ensure the successful start-up of the system with the
individual module starting up at different time. With this
circuitry, each module’s local ISHARE signal is connected to
the system share bus only when it starts switching (finishing
of pre-biased start-up). In addition, when the module is shut
off, its ISHARE signal will be removed from the ISHARE bus.
The validated signal transistors shown in Figure 15 are:
MMBT3904 for Q1 and Q2; 2N7002 for Q3.
With the circuits of Figure 15 implemented, the system can
also be further implemented with the CLKOUT-SYNC
connection to have the modules synchornized and phase-
shifted, which is the third option of system configuration.
However, the lose of CLKOUT signal will cause the
shutdown of the other module receiving the signal.
Compared with the second option (single wire (ISHARE)
connection), this option has one more wire connection, but
all the modules are synchronized and phase-shifted.
In summary, the communication wire connection in parallel
systems offers flexibility. Each configuration option has its
own unique features. The selection of the connections of the
conmmunication wire should be based upon evaluation of
the priorities of system requirements and features, such as
reliability, number of wire connections, synchronizations and
fault tolerance, etc.
R
ISET1
ISET
VSEN1/2- COM1/2
ISHARE
ISL8120
29
R
FIGURE 16. SIMPLIFIED 6-PHASE SINGLE OUTPUT IMPLEMENTATION
ISHARE1
1
SHARE BUS
R
ISET2
ISET
R
VSEN2-
ISHARE_
ISL8120
ISHARE
ISL8120
VCC
R
COM1/2
= R
ISHARE2
2
ISET_
In dual mode, the current sharing block for current sharing of
modules with independant voltage loop is disabled.
Overcurrent Protection
The OCP function is enabled at start-up. When both
channels operate independently, the average function is
disabled and generates zero average current (IAVG = 0).
The Channel 2 current (ICS2) is compared with ITRIP
(108µA) as its own independent overcurrent protection and
the 7 clock cycles delay is bypassed. The Channel 1’s
current (ICS1) plus 15µA offset forms a voltage (VISHARE)
with an external resistor R
precision 1.2V threshold for OCP; while the 108µA OCP
comparator with 7-cycle delay is also activated.
In multiphase operation, the VISHARE represents the average
current of all active channels and compares with the ISHARE
pin precision 1.2V threshold to determine the overcurrent
condition. At the same time, each channel has additional
overcurrent trip point at 108µA with 7-cycle delay for phase
overcurrent protection. This scheme helps protect against loss
of channel(s) in multi-phase mode so that no single channel
could carry more than 108µA in such event. See Figure 13.
Note that it is not necessary for the R
at the same level as the 108µA OCP comparator if the
application allows. Typically the ISHARE pin average current
protection level should be higher than the phase current
protection level. For instance, when Channel 1 operates
independently, the OC trip set by 1.2V comparator can be lower
than 108µA trip point as shown in Equation 6.
where N is the number of phases; NCNTL is the number of
the ISL8120 controllers in parallel or multiphase operations;
R
R
ISHARE
ISEN1
VSEN1-
VSEN1+
=
=
⎛
⎜
⎝
--------------------------------------------------------------------------------------------------------------------- -
I
--------- -
-------------- -
I
OC
1.2V
N
TRIP
+
V
--------------- -
OUT
L
ISET
VSEN1/2- COM1/2
•
R
⎛
⎝
ISET
--------------- - t
2F
ISHARE
1 D
ISHARE
ISL8120
–
I
SW
TRIP
=
R
–
ISHARE3
R
and compares with a
MIN_OFF
ISHARE
3
ISHARE
⎞
⎠
⋅
to be scaled to trip
⎞
⎟
⎠
N
•
CNTL
DCR
R
ISET3
March 20, 2009
(EQ. 6)
FN6641.0