参数资料
| 型号： | ISL62870HRUZ-T |
| 厂商： | Intersil |
| 文件页数： | 9/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 16-TQFN |
| 标准包装： | 3,000 |
| 系列： | Robust Ripple Regulator™ (R³) |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 100% |
| 电源电压： | 3.3 V ~ 25 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -10°C ~ 100°C |
| 封装/外壳： | 16-UFQFN |
| 包装： | 带卷 (TR) |
ISL62870
output voltage (V OUT ) at the VO pin. The positive slope of
V R can be written as Equation 10:
negative when conducting towards the phase node. The DC
component of the inductor current is positive, but the AC
V RPOS = ( g m ) ? ( V IN – V OUT ) ? C R
(EQ. 10)
component known as the ripple current, can be either positive
or negative. Should the sum of the AC and DC components of
V RNEG = g m ? V OUT ? C R
The negative slope of V R can be written as Equation 11:
(EQ. 11)
Where g m is the gain of the transconductance amplifier.
A window voltage V W is referenced with respect to the error
amplifier output voltage V COMP , creating an envelope into
which the ripple voltage V R is compared. The amplitude of
V W is controlled internally by the IC. The V R, V COMP, and
V W signals feed into a window comparator in which V COMP
is the lower threshold voltage and V W is the higher threshold
voltage. Figure 6 shows PWM pulses being generated as V R
traverses the V W and V COMP thresholds. The PWM
switching frequency is proportional to the slew rates of the
positive and negative slopes of V R; it is inversely
proportional to the voltage between V W and V COMP.
the inductor current remain positive for the entire switching
period, the converter is in continuous-conduction-mode (CCM.)
However, if the inductor current becomes negative or zero, the
converter is in discontinuous-conduction-mode (DCM.)
Unlike the standard DC/DC buck regulator, the synchronous
rectifier can sink current from the output filter inductor during
DCM, reducing the light-load efficiency with unnecessary
conduction loss as the low-side MOSFET sinks the inductor
current. The ISL62870 controller avoids the DCM conduction
loss by making the low-side MOSFET emulate the current
blocking behavior of a diode. This smart-diode operation
called diode-emulation-mode (DEM) is triggered when the
negative inductor current produces a positive voltage drop
across the r DS(ON) of the low-side MOSFET for eight
consecutive PWM cycles while the LGATE pin is high. The
converter will exit DEM on the next PWM pulse after
detecting a negative voltage across the r DS(ON) of the low-
RIPPLE CAPACITOR VOLTAGE C R
WINDOW VOLTAGE V W
side MOSFET.
It is characteristic of the R 3 architecture for the PWM
switching frequency to decrease while in DCM, increasing
efficiency by reducing unnecessary gate-driver switching
losses. The extent of the frequency reduction is proportional
to the reduction of load current. Upon entering DEM, the
ERROR AMPLIFIER VOLTAGE V COMP
PWM
FIGURE 6. MODULATOR WAVEFORMS DURING LOAD
TRANSIENT
Synchronous Rectification
A standard DC/DC buck regulator uses a free-wheeling
diode to maintain uninterrupted current conduction through
the output inductor when the high-side MOSFET switches off
for the balance of the PWM switching cycle. Low conversion
efficiency as a result of the conduction loss of the diode
makes this an unattractive option for all but the lowest
current applications. Efficiency is dramatically improved
when the free-wheeling diode is replaced with a MOSFET
that is turned on whenever the high-side MOSFET is turned
off. This modification to the standard DC/DC buck regulator
is referred to as synchronous rectification, the topology
implemented by the ISL62870 controller.
Diode Emulation
The polarity of the output inductor current is defined as positive
when conducting away from the phase node, and defined as
9
PWM frequency is forced to fall approximately 30% by
forcing a similar increase of the window voltage V W . This
measure is taken to prevent oscillating between modes at
the boundary between CCM and DCM. The 30% increase of
V W is removed upon exit of DEM, forcing the PWM switching
frequency to jump back to the nominal CCM value.
Power-On Reset
The IC is disabled until the voltage at the VCC pin has
increased above the rising power-on reset (POR) threshold
voltage V VCC_THR . The controller will become disabled
when the voltage at the VCC pin decreases below the falling
POR threshold voltage V VCC_THF . The POR detector has a
noise filter of approximately 1μs.
VIN and PVCC Voltage Sequence
Prior to pulling EN above the V ENTHR rising threshold
voltage, the following criteria must be met:
1. V PVCC is at least equivalent to the VCC rising power-on
reset voltage V VCC_THR
2. V VIN must be 3.3V or the minimum required by the
application.
Start-Up Timing
Once VCC has ramped above V VCC_THR , the controller can
be enabled by pulling the EN pin voltage above the input high
threshold V ENTHR . Approximately 20μs later, the voltage at the
SREF pin begins slewing to the designated VID set-point. The
FN6708.0
August 14, 2008
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL62871 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:PWM DC/DC Controller With VID Inputs For Portable GPU Core-Voltage Regulator |
| ISL62871HRUZ | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:PWM DC/DC Controller With VID Inputs For Portable GPU Core-Voltage Regulator |
| ISL62871HRUZ-T | 功能描述:IC REG CTRLR BUCK PWM 16-TQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:Robust Ripple Regulator™ (R³) 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL62872HRUZ | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:PWM DC/DC Controller With VID Inputs For Portable GPU Core-Voltage Regulator |
| ISL62872HRUZ-T | 功能描述:IC REG CTRLR BUCK PWM 20-TQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:Robust Ripple Regulator™ (R³) 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
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