參數(shù)資料
型號(hào)： ISL6556BCR-T
廠商： INTERSIL CORP
元件分類： 穩(wěn)壓器
英文描述： Optimized Multi-Phase PWM Controller with 6-Bit DAC and Programmable Internal Temperature Compensation for VR10.X Application
中文描述： SWITCHING CONTROLLER, 1500 kHz SWITCHING FREQ-MAX, PQCC32
封裝： 5 X 5 MM, PLASTIC, MO-220VHHD-2, QFN-32
文件頁(yè)數(shù)： 15/24頁(yè)
文件大?。?/td> 692K
代理商： ISL6556BCR-T
15
FN9097.4
December 28, 2004
on-the-fly VID changes in a controlled manner. Supervising
the safe output voltage transition within the DAC range of the
processor without discontinuity or disruption is a necessary
function of the core-voltage regulator.
The ISL6556B checks the VID inputs six times every
switching cycle. If the VID code is found to have changed,
the controller waits half of a complete cycle before executing
a 12.5mV change. If during the half-cycle wait period, the
difference between DAC level and the new VID code
changes sign, no change is made. If the VID code is more
than 1 bit higher or lower than the DAC (not recommended),
the controller will execute 12.5mV changes six times per
cycle until VID and DAC are equal. It is for this reason that it
is important to carefully control the rate of VID stepping in 1-
bit increments.
In order to ensure the smooth transition of output voltage
during VID change, a VID step change smoothing network is
required for an ISL6556B based voltage regulator. This
network is composed by a 1k
internal resistor between the
output of DAC and the C
REF
between REF pin to ground.
The selection of C
REF
is based on the time duration for 1 bit
VID change and the allowable delay time.
Assuming the microprocessor controls the VID change at 1
bit every T
VID
, the relationship between C
REF
and T
VID
is
given by Equation 9.
As an example, for
a VID step change rate of 5
μ
s per bit, the
value of C
REF
is 22nF based on Equation 9.
Temperature Compensation
The MOSFET r
DS(ON)
varies in proportion to varying
temperature. This means that a circuit using r
DS(ON)
to
sense channel current is subject to a corresponding error in
current measurement. In order to compensate for this
temperature-related error, a temperature compensation
circuit is provided within ISL6561. This circuit senses the
internal IC temperature and, based on a resistor-selectable
scaling factor, adjust the droop current flow to the FB pin.
When the TCOMP resistor is properly selected, the droop
current can accurately represent the load current to achieve
a linear, temperature-independant load line.
The value of the Tcomp resistor can be determined using
Equation 10.
T
TC
In Equation 10,
K
T
is the temperature coupling coefficient
between the ISL6561 and the lower MOSFET. It represents
how closely the controller temperature tracks the lower
MOSFET temperature. The value of K
T
is typically between
75% and 100%. K
TC
is the temperature dependant
transconductance of internal compensation circuit. Its value
is designed as 1
μ
A/V/°C. The temperature coefficient of
MOSFET
r
DS(ON)
is given by . This is the ratio of the
change in resistance and the change in temperature.
Resistance is normalized to the value at 25°C and the value
of is typically between 0.35%/°C and 0.50%/°C.
α
According to Equation 10,
a voltage regulator with 80%
thermal coupling coefficient between the controller and lower
MOSFET and 0.4%
/°C
temperature coefficient of MOSFET
r
DS(ON)
requires a 5k
TCOMP resistor.
Initialization
Prior to initialization, proper conditions must exist on the
enable inputs and VCC. When the conditions are met, the
controller begins soft-start. Once the output voltage is within
the proper window of operation, PGOOD asserts logic.
Enable and Disable
While in shutdown mode, the PWM outputs are held in a
high-impedance state to assure the drivers remain off. The
following input conditions must be met before the ISL6556B
is released from shutdown mode.
1. The bias voltage applied at VCC must reach the internal
power-on reset (POR) rising threshold. Once this
threshold is reached, proper operation of all aspects of
the ISL6556B is guaranteed. Hysteresis between the
rising and falling thresholds assure that once enabled,
the ISL6556B will not inadvertently turn off unless the
bias voltage drops substantially (see
Electrical
Specifications
).
2. The ISL6556B features an enable input (EN) for power
sequencing between the controller bias voltage and
another voltage rail. The enable comparator holds the
ISL6556B in shutdown until the voltage at EN rises above
1.24V. The enable comparator has about 100mV of
hysteresis to prevent bounce. It is important that the
C
REF
0.004X T
VID
=
(EQ. 9)
(EQ. 10)
R
TCOMP
---------------------
=
α
FIGURE 8. POWER SEQUENCING USING THRESHOLD-
SENSITIVE ENABLE (EN) FUNCTION
-
+
1.24V
EXTERNAL CIRCUIT
ISL6556B INTERNAL CIRCUIT
EN
+12V
POR
CIRCUIT
10.7k
1.40k
ENABLE
COMPARATOR
SOFT-START
AND
FAULT LOGIC
ENLL
(ISL6556BCR ONLY)
VCC
ISL6556B
相關(guān)PDF資料
PDF描述
ISL6556BCBZA-T Optimized Multi-Phase PWM Controller with 6-Bit DAC and Programmable Internal Temperature Compensation for VR10.X Application
ISL6556BCR Optimized Multi-Phase PWM Controller with 6-Bit DAC and Programmable Internal Temperature Compensation for VR10.X Application
ISL6556BCRZ Optimized Multi-Phase PWM Controller with 6-Bit DAC and Programmable Internal Temperature Compensation for VR10.X Application
ISL6556B Optimized Multi-Phase PWM Controller with 6-Bit DAC and Programmable Internal Temperature Compensation for VR10.X Application
ISL6556BCB PWM Controller with Wide Input Range 8-SOIC -40 to 125
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ISL6557 WAF 制造商:Intersil Corporation 功能描述:
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