ISL6537ACRZ Intersil, ISL6537ACRZ Datasheet - Page 8

• Manufacturer Part Number: ISL6537ACRZ
• Description: IC REG/CTRLR ACPI DUAL DDR 28QFN
• Manufacturer: Intersil

Specifications of ISL6537ACRZ

• Applications: Memory, DDR/DDR2 Regulator
• Current - Supply: 7mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -

FB2 (Pin 18)
Connect the output of the V
this pin through a properly sized resistor divider. The voltage
at this pin is regulated to 0.8V. This pin is monitored for
undervoltage events.
DRIVE2 (Pin 10)
This pin provides the gate voltage for the V
linear regulator pass transistor. Connect this pin to the gate
terminal of an external N-Channel MOSFET transistor.
FB3 (Pin 18)
Connect the output of the DAC linear regulator to this pin
through a properly sized resistor divider. The voltage at this
pin is regulated to 0.8V.
DRIVE3 (Pin 10)
This pin provides the gate voltage for the DAC linear
regulator pass transistor. Connect this pin to the gate
terminal of an external N-Channel MOSFET transistor.
VIDPGD (Pin 12)
The VIDPGD pin is an open-drain logic output that changes
to a logic low if the V
regulation in S0/S1/S2 state. VIDPGD will always be low in
any state other than S0/S1/S2.
SLP_S5# (Pin 23)
This pin accepts the SLP_S5# sleep state signal.
SLP_S3# (Pin 2)
This pin accepts the SLP_S3# sleep state signal.
Functional Description
Overview
The ISL6537A provides complete control, drive, protection
and ACPI compliance for regulator powering DDR memory
systems and the GMCH core and GMCH/CPU termination
rails. It is primarily designed for computer applications
powered from an ATX power supply.
A 250kHz Synchronous Buck Regulator with a precision
0.8V reference provides the proper Core voltage to the
system memory of the computer. An internal LDO regulator
with the ability to both sink and source current and an
externally available buffered reference that tracks the V
output by 50% provides the V
A second 250kHz PWM Buck regulator, which requires an
external MOSFET driver, provides the GMCH core voltage.
This PWM regulator is +180° out of phase with the PWM
regulator used for the Memory core. Two additional LDO
controllers are included, one for the regulation of the
GMCH/CPU termination rail and the second for the DAC.
ACPI compliance is realized through the SLP_S3 and
SLP_S5 sleep signals and through monitoring of the 12V
ATX bus.
TT_GMCH/CPU
TT_GMCH/CPU
TT
8
termination voltage.
linear regulator is out of
linear regulator to
TT_GMCH/CPU
DDQ
ISL6537A
Initialization
The ISL6537A automatically initializes upon receipt of input
power. Special sequencing of the input supplies is not
necessary. The Power-On Reset (POR) function continually
monitors the input bias supply voltages. The POR monitors
the bias voltage at the 5VSBY and P12V pins. The POR
function initiates soft-start operation after the bias supply
voltages exceed their POR thresholds.
ACPI State Transitions
Figure 1 shows how the individual regulators are controlled
during all state transitions. All references to timing in this
section are in reference to Figure 1.
Cold Start (S4/S5 to S0 Transition)
At the onset of a mechanical start, time t
ISL6537A receives its bias voltage from the 5V Standby bus
(5VSBY). Once the 5VSBY rail has exceeded the POR
threshold, the ISL6537A will remain in an internal S5 state
until both the SLP_S3 and SLP_S5 signal have transitioned
high and the 12V POR threshold has been exceeded by the
+12V rail from the ATX, which occurs at time t
Once all of these conditions are met, the PWM error
amplifiers will first be reset by internally shorting the COMP
pins to the respective FB pins. This reset lasts for three soft-
start cycles, which is typically 24ms (one soft-start cycle is
typically 8.2ms). The digital soft-start sequence will then
begin. Each regulator is enabled and soft-started according
to a preset sequence.
At time t
V
The digital soft-start for both PWM regulators is accomplished
by clamping the error amplifier reference input to a level
proportional to the internal digital 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 linear regulators, with the exception of the internal
V
error amplifier reference is clamped to the internal digital
soft-start voltage. As the soft-start voltage ramps up, the
respective DRIVE pin voltages increase, thus enhancing the
N-MOSFETs and charging the output capacitors in a
controlled manner.
At time t
V
regulation and the V
regulators are soft-started. At time t
rail and DAC rails are in regulation and the V
regulator is soft-started.
The V
regulators. When the V
reference is internally shorted to the V
DDQ_DDR
TT_DDR
GMCH
TT_DDR
2
3
rail is soft-started. At time t
, the 3 soft-start cycle reset has ended and the
, the V
LDO, are soft-started in a similar manner. The
rail is digitally soft-started.
LDO soft-starts in a manner unlike the other
DDQ_DDR
TT_GMCH/CPU
TT_DDR
rail is in regulation and the
regulator is disabled, the
4
5
and the DAC linear
, the V
, the V
TT_DDR
0
in Figure 1, the
GMCH
TT_GMCH/CPU
TT_DDR
1
output. This
.
rail is in
internal
FN9143.5