isl6530 Intersil Corporation, isl6530 Datasheet - Page 7
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isl6530
Manufacturer Part Number
isl6530
Description
Dual 5v Synchronous Buck Pulse-width Modulator Pwm Controller For Ddram Memory Vddq And Vtttermination
Manufacturer
Intersil Corporation
Datasheet
1.ISL6530.pdf
(17 pages)
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While the V
V
via the SENSE2 pin. The window regulator can overcome up
to at least ±10mA of leakage on V
While V2_SD is high, PGOOD is low.
PHASE1 and PHASE2
Connect PHASE1 and PHASE2 to the corresponding upper
MOSFET source. This pin is used as part of the upper
MOSFET bootstrapped drives. PHASE1 is used to monitor
the voltage drop across the upper MOSFET of the V
regulator for over-current protection. The PHASE1 pin is
monitored by the adaptive shoot through protection circuitry
to determine when the upper FET of the V
turned off.
FB1, COMP1, FB2, and COMP2
COMP1, COMP2, FB1, and FB2 are the available external
pins of the error amplifiers. The FB1 and FB2 pins are the
inverting inputs of each error amplifier and the COMP1 and
COMP2 pins are the associated outputs. An appropriate AC
network across these pins is used to compensate the
voltage-controlled feedback loop of each converter.
VREF and VREF_IN
VREF produces a voltage equal to one half of the voltage on
SENSE1. This low current output is connected to the VREF
input of the DDRAM devices being powered. This same
voltage is used as the reference input of the V
amplifier. Thus V
VREF_IN is used as an option to overdrive the internal
resistor divider network that sets the voltage for both
VREF_OUT and the reference voltage for the V
100pF capacitor between VREF_IN and ground is
recommended for proper operation.
PVCC1
This is the positive supply for the lower gate driver, LGATE1.
PVCC1 is connected to a well decoupled 5V.
SENSE1 and SENSE2
Both SENSE1 and SENSE2 are connected directly to the
regulated outputs of the V
respectively. SENSE1 is used as an input to create the
voltage at VREF_OUT and the reference voltage for the V
supply. SENSE2 is used as the regulation point for the
window regulator that is enabled in V2_SD mode.
Functional Description
Overview
The ISL6530 contains control and drive circuitry for two
synchronous buck PWM voltage regulators. Both regulators
utilize 5V bootstrapped output topology to allow use of low
cost N-channel MOSFETs. The regulators are driven by
DDQ
via a low current window regulator which drives V
TT
supply “floats”, it is held to about 50% of
TT
is controlled to 50% of V
DDQ
7
and V
TT
.
TT
supplies,
DDQ
DDQ
TT
supply has
TT
.
error
supply. A
DDQ
TT
TT
ISL6530
300kHz clocks. The clocks are phase locked and displaced
90
The first regulator includes a precision 0.8V reference and is
intended to provide the proper V
system. The V
protection utilizing the r
Following a fault condition, the V
via a digital softstart circuit.
Included in the ISL6530 is a precision V
output. V
is derived via a precision internal resistor divider connected
to the SENSE1 terminal.
The second PWM regulator is designed to provide V
termination for the DDRAM signal lines. The reference to the
V
termination voltage equal to .5xV
MOSFET of the V
V
sinking and sourcing current on the V
Two benefits result from the ISL6530 dual controller
topology. First, as VREF is always .5xV
will track the V
the overcurrent protection incorporated into the V
will simultaneously protect the V
Initialization
The ISL6530 automatically initializes upon application of
input power. Special sequencing of the input supplies is not
necessary. The Power-On Reset (POR) function continually
monitors the input bias supply voltage at the VCC pin. The
POR function initiates soft-start operation after the 5V bias
supply voltage exceeds its POR threshold.
Soft-Start
The POR function initiates the digital soft start sequence. The
PWM error amplifier reference input for the VDDQ regulator is
clamped to a level proportional to the soft-start voltage. As the
soft-start voltage slews up, the PWM comparator generates
PHASE pulses of increasing width that charge the output
capacitor(s). This method provides a rapid and controlled
output voltage rise. The soft start sequence typically takes
about 7ms.
With the V
automatically track the ramp of the V
enabling a soft-start for V
Figure 2 shows the soft-start sequence for a typical application.
At t0, the +5V VCC bias voltage starts to ramp. Once the
voltage on VCC crosses the POR threshold at time t1, both
outputs begin their soft-start sequence. The triangle waveforms
from the PWM oscillators are compared to the rising error
amplifier output voltage. As the error amplifier voltage
increases, the pulse-widths on the UGATE pins increase to
reach their steady-state duty cycle at time t2.
TT
DDQ
o
to minimize noise coupling between the controllers.
regulator is V
voltage. The V
REF
TT
regulator reference held at
is a buffered representation of .5xV
DDQ
DDQ
TT
REF
controller implements overcurrent
supply during softstart cycles. Second,
TT
supply is connected to the regulated
. Thus the V
DS(ON)
controller is designed to enable both
TT
.
of the upper MOSFET.
DDQ
TT
DDQ
DDQ
TT
supply.
DDQ
regulator provides a
. The drain of the upper
to a DDRAM memory
regulator is softstarted
TT
DDQ
REF
rail.
1
-- - V
2
softstart, thus
⋅
, the V
reference
DDQ
November 15, 2004
DDQ
DDQ
TT
it will
TT
. V
supply
supply
FN9052.2
REF