- 您现在的位置：买卖IC网 > PDF目录22319 > MAX1777EEI+T (Maxim Integrated)IC REG QD BUCK/LINEAR 28QSOP PDF资料下载
参数资料
| 型号： | MAX1777EEI+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 20/32页 |
| 文件大小： | 0K |
| 描述： | IC REG QD BUCK/LINEAR 28QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 拓扑： | 降压（降压）（2），线性（LDO）（2） |
| 功能： | 任何功能 |
| 输出数： | 4 |
| 频率 - 开关： | 200kHz ~ 500kHz |
| 电压/电流 - 输出 1： | 控制器 |
| 电压/电流 - 输出 2： | 控制器 |
| 电压/电流 - 输出 3： | 3.3V，100mA |
| 带 LED 驱动器： | 无 |
| 带监控器： | 无 |
| 带序列发生器： | 是 |
| 电源电压： | 4.5 V ~ 24 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 28-QSOP |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页当前第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
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
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| LM4040C41ILPR | IC VREF SHUNT PREC 4.096V TO92-3 |
| V300C3V3H50BG | CONVERTER MOD DC/DC 3.3V 50W |
| MAX786CAI+T | IC REG QD BCK/LINEAR SYNC 28SSOP |
| HE3C243M050BZSS | CAP TANT 24000UF 50V 20% RADIAL |
| MAX5093AATE+ | IC REG DL BUCK/LINEAR 16TQFN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1778EUG | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EUG+ | 功能描述:直流/直流开关转换器 Quad-Output TFT LCD w/Buffer RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EUG+T | 功能描述:直流/直流开关转换器 Quad-Output TFT LCD w/Buffer RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EUG-T | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1778EVKIT | 功能描述:电源管理IC开发工具 MAX1778/80/81/82 Eval Kit 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 |
发布紧急采购，3分钟左右您将得到回复。