参数资料
型号: IR3500MTRPBF
厂商: International Rectifier
文件页数: 12/47页
文件大小: 0K
描述: IC XPHASE3 CONTROLLER 32-MLPQ
产品变化通告: (EP) Parts Discontinuation 25/May/2012
标准包装: 1
系列: XPhase3™
应用: 处理器
电流 - 电源: 6.5mA
电源电压: 4.75 V ~ 7.5 V
工作温度: 0°C ~ 100°C
安装类型: 表面贴装
封装/外壳: 32-VFQFN 裸露焊盘
供应商设备封装: 32-MLPQ(5x5)
包装: 标准包装
产品目录页面: 1383 (CN2011-ZH PDF)
其它名称: IR3500MTRPBFDKR
IR3500
v C ( s ) = v L ( s )
1
1 + sR CS C CS
= i L ( s )
R L + sL
1 + sR CS C CS
Usually the resistor Rcs and capacitor Ccs are chosen so that the time constant of Rcs and Ccs equals the time
constant of the inductor which is the inductance L over the inductor DCR (R L ). If the two time constants match, the
voltage across Ccs is proportional to the current through L, and the sense circuit can be treated as if only a sense
resistor with the value of R L was used. The mismatch of the time constants does not affect the measurement of
inductor DC current, but affects the AC component of the inductor current.
v L
i L
Current
Sense Amp
L
R CS
R L
C CS
c
v CS
V O
C O
CSOUT
Figure 7 - Inductor Current Sensing and Current Sense Amplifier
The advantage of sensing the inductor current versus high side or low side sensing is that actual output current
being delivered to the load is obtained rather than peak or sampled information about the switch currents. The
output voltage can be positioned to meet a load line based on real time information. Except for a sense resistor in
series with the inductor, this is the only sense method that can support a single cycle transient response. Other
methods provide no information during either load increase (low side sensing) or load decrease (high side sensing).
An additional problem associated with peak or valley current mode control for voltage positioning is that they suffer
from peak-to-average errors. These errors will show in many ways but one example is the effect of frequency
variation. If the frequency of a particular unit is 10% low, the peak to peak inductor current will be 10% larger and
the output impedance of the converter will drop by about 10%. Variations in inductance, current sense amplifier
bandwidth, PWM prop delay, any added slope compensation, input voltage, and output voltage are all additional
sources of peak-to-average errors.
Current Sense Amplifier
A high speed differential current sense amplifier is located in the phase IC, as shown in Figure 7. Its gain is
nominally 32.5 and the 3850 ppm/oC increase in inductor DCR should be compensated in the voltage loop feedback
path.
The current sense amplifier can accept positive differential input up to 50mV and negative up to -10mV before
clipping. The output of the current sense amplifier is summed with the DAC voltage and sent to the control IC and
other phases through an on-chip 3K
resistor connected to the ISHARE pin. The ISHARE pins of all the phases are
tied together and the voltage on the share bus represents the average current through all the inductors and is used
by the control IC for voltage positioning and current limit protection. The input offset of this amplifier is calibrated to
+/- 1mV in order to reduce the current sense error.
The input offset voltage is the primary source of error for the current share loop. In order to achieve very small input
offset error and superior current sharing performance, the current sense amplifier continuously calibrates itself. This
calibration algorithm creates ripple on ISHARE bus with a frequency of fsw / 896 in a multiphase architecture.
Page 12 of 47
May 18, 2009
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