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| 型号： | MAX1977EEI+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/32页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR PS QUAD HI EFF 28QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 4.5 V ~ 24 V |
| 输出数： | 4 |
| 输出电压： | 3.3V，5V，2 V ~ 5.5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-QSOP |
| 供应商设备封装： | 28-QSOP |
| 包装： | 管件 |
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High-Efficiency, Quad Output, Main Power-
Supply Controllers for Notebook Computers
Reference and Linear Regulators
(REF, LDO5, and LDO3)
The 2V reference (REF) is accurate to ±1% over tem-
perature, making REF useful as a precision system ref-
erence. Bypass REF to GND with a 0.22μF minimum
capacitor. REF can supply up to 100μA for external
loads. However, if extremely accurate specifications for
both the main output voltages and REF are essential,
avoid loading REF. Loading REF reduces the LDO5,
LDO3, OUT5, and OUT3 output voltages slightly,
because of the reference load-regulation error.
Two internal regulators produce 5V (LDO5) and
3.3V(LDO3). LDO5 provides gate drive for the external
MOSFETs and powers the PWM controller, logic, refer-
ence, and other blocks within the device. The LDO5
regulator supplies a total of 100mA for internal and
external loads, including MOSFET gate drive, which
typically varies from 10mA to 50mA, depending on
switching frequency and the external MOSFETs. LDO3
supplies up to 100mA for external loads. Bypass LDO5
and LDO3 with a minimum of 4.7μF load, use an addi-
tional 1μF per 5mA of internal and external load.
When the 5V main output voltage is above the LDO5
bootstrap-switchover threshold, an internal 1.4 ? P-chan-
nel MOSFET switch connects OUT5 to LDO5, while simul-
taneously shutting down the LDO5 linear regulator.
Similarly, when the 3.3V main output voltage is above the
LDO3 bootstrap-switchover threshold, an internal 1.5 ?
P-channel MOSFET switch connects OUT3 to LDO3,
while simultaneously shutting down the LDO3 linear regu-
lator. These actions bootstrap the device, powering the
internal circuitry and external loads from the output SMPS
voltages, rather than through linear regulators from the
battery. Bootstrapping reduces power dissipation due to
gate charge and quiescent losses by providing power
from a 90%-efficient switch-mode source, rather than
from a much-less-efficient linear regulator.
Current Limit Circuit (ILIM_)
The current-limit circuit employs a “valley” current-sens-
ing algorithm. The MAX1999 uses the on-resistance of
the synchronous rectifier, while the MAX1777/MAX19777
uses a discrete resistor in series with the source of the
synchronous rectifier as a current-sensing element. If the
magnitude of the current-sense signal at CS_
(MAX1777/MAX1977) / LX_ (MAX1999) is above the cur-
rent-limit threshold, the PWM is not allowed to initiate a
new cycle (Figure 6). The actual peak current is greater
than the current-limit threshold by an amount equal to the
inductor ripple current. Therefore, the exact current-limit
characteristic and maximum load capability are a func-
tion of the current-limit threshold, inductor value, and
input and output voltage.
For the MAX1777/MAX1977, connect CS_ to the junction
of the synchronous rectifier source and a current-sense
resistor to GND. With a current-limit threshold of 100mV,
the accuracy is approximately ±7%. Using a lower cur-
rent-sense threshold results in less accuracy. The cur-
rent-sense resistor only dissipates power when the
synchronous rectifier is on.
For lower power dissipation, the MAX1999 uses the on-
resistance of the synchronous rectifier as the current-
sense element (Figure 7). Use the worst-case maximum
value for R DS(ON) from the MOSFET data sheet, and
add some margin for the rise in R DS(ON) with tempera-
ture. A good general rule is to allow 0.5% additional
resistance for each °C of temperature rise. The current
limit varies with the on-resistance of the synchronous
rectifier. The reward for this uncertainty is robust, loss-
less overcurrent sensing. When combined with the
undervoltage protection circuit, this current-limit
method is effective in almost every circumstance.
-I PEAK
MAX1999
DH_
V+
I LOAD
I LIMIT
LX_
DL_
OUT_
0
TIME
Figure 7. Current Sensing Using R DS(ON) of Synchronous
Figure 6. “Valley” Current-Limit Threshold Point
Rectifier
20
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1977EEI+ | 功能描述:DC/DC 开关控制器 Quad Out Main Power Supply Controller 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 |
| MAX1977EEI+T | 功能描述:DC/DC 开关控制器 Quad Out Main Power Supply Controller 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 |
| MAX1977EEI-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 |
| MAX1977EEI-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1978ETM | 功能描述:电压模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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