- 您現在的位置：買賣IC網 > PDF目錄383334 > MAX1977EEI (MAXIM INTEGRATED PRODUCTS INC) High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers PDF資料下載
參數資料
| 型號： | MAX1977EEI |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers |
| 中文描述： | DUAL SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | 0.150 INCH, 0.025 INCH PITCH, QSOP-28 |
| 文件頁數： | 20/32頁 |
| 文件大小： | 497K |
| 代理商： | MAX1977EEI |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁當前第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁
M
High-Effic ienc y, Quad Output, Main Power-
S upply Controllers for Notebook Computers
20
______________________________________________________________________________________
Referenc e 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 Circ uit (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
I
LIMIT
I
LOAD
0
TIME
-I
PEAK
Figure 6. “Valley” Current-Limit Threshold Point
MAX1999
V+
DH_
DL_
LX_
OUT_
Figure 7. Current Sensing Using R
DS(ON)
of Synchronous
Rectifier
相關PDF資料 |
PDF描述 |
|---|---|
| MAX1999EEI | High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers |
| MAX1778 | 32-Bit Digital Signal Controller with ROM 100-LQFP -40 to 85 |
| MAX1880 | Quad-Output TFT LCD DC-DC Converters with Buffer |
| MAX1881 | Quad-Output TFT LCD DC-DC Converters with Buffer |
| MAX1882 | Quad-Output TFT LCD DC-DC Converters with Buffer |
相關代理商/技術參數 |
參數描述 |
|---|---|
| MAX1977EEI+ | 功能描述:DC/DC 開關控制器 Quad Out Main Power Supply Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MAX1977EEI+T | 功能描述:DC/DC 開關控制器 Quad Out Main Power Supply Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MAX1977EEI-T | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體: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:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
發(fā)布緊急采購，3分鐘左右您將得到回復。