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| 型号： | MAX1937EEI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 16/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM HYBRID 28-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 混合物 |
| 输出数： | 1 |
| 频率 - 最大： | 500kHz |
| 占空比： | 50% |
| 电源电压： | 6 V ~ 24 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： | 无 |
| 工作温度： | 0°C ~ 85°C |
| 封装/外壳： | 28-QSOP |
| 包装： | 带卷 (TR) |
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
MOSFET Drivers
The DH_ and DL_ drivers are optimized for driving large
high-side (N1 and N2) and larger low-side MOSFETs
(N3 and N4). This is consistent with the low duty-cycle
operation of the controller. The DL_ low-side drive wave-
form is always the complement of the DH_ high-side
drive waveform, with a fixed dead-time between one
MOSFET turning off and the other turning on to prevent
cross-conduction or shoot-through current.
The internal transistor that drives DL_ low is robust with
a 0.5 Ω (typ) on-resistance. This helps prevent DL_ from
being pulled up during the fast rise time of the LX_
node due to capacitive coupling from the drain to the
gate of the low-side synchronous-rectifier MOSFET.
However, some combinations of high-side and low-side
MOSFETs may cause excessive gate-drain coupling,
leading to poor efficiency, EMI, and shoot-through cur-
rents. This is often remedied by adding a resistor (typi-
cally less than 5 Ω ) in series with BST_, which increases
the turn-on time of the high-side MOSFET without
degrading the turn-off time.
Current-Limit Circuit
The MAX1937/MAX1938/MAX1939 use either the on-
resistance of the low-side MOSFETs or a current-sense
resistor to monitor the inductor current. Using the low-
side MOSFETs’ on-resistance as the current-sense ele-
ment provides a lossless and inexpensive solution ideal
for high-efficiency or cost-sensitive applications. The dis-
advantage to this method is that the on-resistance of
MOSFETs vary from part to part, and overtemperature,
which means it cannot be counted on for high accuracy.
If high accuracy is needed, use current-sense resistors,
which provide an accurate current limit under all condi-
tions but reduce efficiency slightly because of the power
lost in the resistors.
The current-limit circuit employs a “valley ” current-
sensing algorithm to monitor the inductor current. If the
current-sense signal does not drop below the current-
limit threshold, the controller does not initiate a new
cycle. This limits the maximum value of I VALLEY to the
current set by the current-limit threshold (Figure 2).
The current-limit threshold is adjustable over a wide
range, allowing for a range of current-sense resistor
values. The voltage on ILIM sets the current-limit
threshold between PGND and CS_ to 0.1 ? V ILIM . The
10mV to 200mV adjustment range corresponds to ILIM
voltages from 100mV to 2V. The ILIM voltage is set by a
resistor-divider between REF and GND. See the Setting
the Current Limit section for details.
Current Balancing
The DC current balancing between phases depends on
the accuracy of the current-sense elements and the off-
set of the current-balance amplifier.
The maximum offset of the current-balance amplifier
(V CBOFFSET ) is ±3mV. The current-balance accuracy
can be calculated from:
Current-balance accuracy = V CBOFFSET / (I L ? R CS )
where I L is the peak inductor current and R CS is the
value of the current-sense resistor.
The current-balance accuracy is most important at full
load. With a load current of 50A (I L = 25A) and 2m Ω
current-sense resistors, the worst-case current-balance
accuracy is:
Current-balance accuracy = 0.003 / (25 ? 0.002) = 6%
If the on-resistance of the low-side MOSFETs is used
for current sensing, the part-to-part variation of the
MOSFET on-resistance is a significant factor in the cur-
rent balance. The matching between MOSFETs should
be on the order of 15%, worst case. Thus, even if the
current-balance amplifier has no offset, the DC-current
balance could be as bad as 15%. In practice, a little
help is received from the thermal ballasting of the
MOSFETs. That is to say, the positive temperature coef-
ficient of the on-resistance of MOSFETs reduces the
mismatch current between the two phases.
Voltage Positioning (VPOS)
During a load transient, the output voltage instantly
changes by the ESR of the output capacitors times the
change in load current ( Δ V OUT = -ESR COUT ? Δ I LOAD ).
Conventional DC-DC converters respond by regulating
the output voltage back to its nominal state after the
load transient occurs (Figure 3). However, the CPU
requires that the output voltage remain within a specific
voltage band. Dynamically positioning the output volt-
age allows the use of fewer output capacitors and
reduces power consumption under heavy load.
For a conventional (nonvoltage-positioned) circuit, the
total output voltage deviation from light load to full load
and back to light load is:
V P-P1 = 2 ? (ESR COUT ? Δ I LOAD ) + V SAG + V SOAR
where V SAG and V SOAR are defined in the Output
Capacitor Selection section. Setting the converter to
regulate at a lower voltage when under load allows a
larger voltage step when the output current suddenly
decreases. The total voltage change for a voltage-posi-
tioned circuit is:
V P-P2 = (ESR COUT ? Δ I LOAD ) + V SAG +V SOAR
16
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1937EEI-TG069 | 制造商:Maxim Integrated Products 功能描述: |
| MAX1938EEI | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1938EEI-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1938EEI-TG069 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1938EVKIT | 功能描述:电源管理IC开发工具 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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