参数资料
| 型号： | ISL95870BHRZ-T |
| 厂商： | Intersil |
| 文件页数： | 20/28页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR PWM 1PHASE GPU 20QFN |
| 标准包装： | 6,000 |
| 应用： | 控制器，GPU 内核电源 |
| 输入电压： | 3.3 V ~ 25 V |
| 输出数： | 1 |
| 输出电压： | 0.5 V ~ 5 V |
| 工作温度： | -10°C ~ 100°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-VFQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN（3x4） |
| 包装： | 带卷 (TR) |
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ISL95870, ISL95870A, ISL95870B
The dotted red and blue lines in Figure 16 represent the time
delayed behavior of V OUT and V COMP in response to a load
transient when an integrator is used. The solid red and blue lines
illustrate the increased response of R 4 in the absence of the
integrator capacitor.
Diode Emulation
The polarity of the output inductor current is defined as positive
PHASE
8.5μA
OCSET
DCR
+
R OCSET
+ V ROCSET
L
V DCR
C SEN
_
I L
_
V O
C O
when conducting away from the phase node, and defined as
negative when conducting towards the phase node. The DC
component of the inductor current is positive, but the AC
VO
R O
component known as the ripple current, can be either positive or
negative. Should the sum of the AC and DC components of 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).
FIGURE 17. OVERCURRENT PROGRAMMING CIRCUIT
Figure 17 shows the overcurrent set circuit. The inductor consists
of inductance L and the DC resistance DCR. The inductor DC
current I L creates a voltage drop across DCR, which is given by
Equation 31:
Unlike the standard DC/DC buck regulator, the synchronous
V DCR = I L ? DCR
(EQ. 31)
V ROCSET = 8.5 μ A ? R OCSET
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 ISL95870, ISL95870A, ISL95870B controllers avoid
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-side MOSFET.
It is characteristic of the R 4 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 PWM frequency is forced to fall
The I OCSET current source sinks 8.5μA into the OCSET pin,
creating a DC voltage drop across the resistor R OCSET , which is
given by Equation 32:
(EQ. 32)
The DC voltage difference between the OCSET pin and the VO pin,
which is given by Equation 33:
V OCSET – V VO = V DCR – V ROCSET = I L ? DCR – I OCSET ? R OCSET
(EQ. 33)
The IC monitors the voltage of the OCSET pin and the VO pin.
When the voltage of the OCSET pin is higher than the voltage of
the VO pin for more than 10μs, an OCP fault latches the
converter off.
The value of R OCSET is calculated with Equation 34, which is
written as:
R OCSET = ----------------------------
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%
I OC ? DCR
I OCSET
(EQ. 34)
increase of V W is removed upon exit of DEM, forcing the PWM
switching frequency to jump back to the nominal CCM value.
Overcurrent
The overcurrent protection (OCP) setpoint is programmed with
resistor R OCSET , which is connected across the OCSET and
PHASE pins. Resistor R O is connected between the VO pin and
the actual output voltage of the converter. During normal
operation, the VO pin is a high impedance path, therefore there is
no voltage drop across R O . The value of resistor R O should always
match the value of resistor R OCSET .
Where:
- R OCSET ( Ω ) is the resistor used to program the overcurrent
setpoint
- I OC is the output DC load current that will activate the OCP
fault detection circuit
- DCR is the inductor DC resistance
For example, if I OC is 20A and DCR is 4.5m Ω , the choice of
R OCSET is equal to 20A x 4.5m Ω /8.5μA = 10.5k Ω.
Resistor R OCSET and capacitor C SEN form an R-C network to
sense the inductor current. To sense the inductor current
correctly not only in DC operation, but also during dynamic
operation, the R-C network time constant R OCSET C SEN needs to
match the inductor time constant L/DCR. The value of C SEN is
then written as Equation 35:
C SEN = ------------------------------------------
L
R OCSET ? DCR
(EQ. 35)
For example, if L is 1.5μH, DCR is 4.5m Ω , and R OCSET is 9k Ω, the
choice of C SEN = 1.5μH/(9k Ω x 4.5m Ω ) = 0.037μF .
20
FN6899.1
December 2, 2013
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL95870BHRZ-TS2490 | 制造商:Intersil Corporation 功能描述:IBM, ISL95870BHRZ-T W/CONTAINER LABELING - Tape and Reel |
| ISL95870BHRZ-TS2568 | 制造商:Intersil Corporation 功能描述:INTEL, ISL95870BHRTZ-T W/BARCODE LABELS, 12 MONTH D/C RESTRI - Tape and Reel |
| ISL95870BIRZ | 功能描述:电流型 PWM 控制器 0/2 BIT PWM GPU CONTLR FOR NOTEBOOK RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| ISL95870BIRZ-T | 功能描述:电流型 PWM 控制器 0/2 BIT PWM GPU CONTLR FOR NOTEBOOK RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| ISL95870HRUZ-T | 功能描述:电流型 PWM 控制器 0/2 BIT PWM GPU CONTLR FOR NOTEBOOK RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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