- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385505 > LTC1704 (Linear Technology Corporation) Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 PDF資料下載
參數(shù)資料
| 型號： | LTC1704 |
| 廠商： | Linear Technology Corporation |
| 元件分類： | 通用總線功能 |
| 英文描述： | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
| 中文描述： | 550kHz的同步開關(guān)穩(wěn)壓器控制器加線性穩(wěn)壓控制器 |
| 文件頁數(shù)： | 23/28頁 |
| 文件大小： | 343K |
| 代理商： | LTC1704 |
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頁第20頁第21頁第22頁當(dāng)前第23頁第24頁第25頁第26頁第27頁第28頁
LTC1704/LTC1704B
23
1704bfa
APPLICATIU
External ground drops aren’t so negligible. The LTC1704
can sense the positive end of the output voltage by
attaching the feedback resistor directly at the load, but it
cannot do the same with the ground lead. Just 0.001
of
resistance in the ground lead at 10A load will cause a 10mV
error in the output voltage—as much as all the other DC
errors put together. Proper layout becomes essential to
achieving optimum load regulation from the LTC1704. A
properly laid out LTC1704 circuit should move less than a
millivolt at the output from zero to full load.
W
U
U
Transient Response
Transient response is the other half of the regulation
equation. The LTC1704 can keep the DC output voltage
constant to within 1% when averaged over hundreds of
cycles. Over just a few cycles, however, the external
components conspire to limit the speed that the output
can move. Consider a typical 5V to 1.5V circuit, subjected
to a 1A to 5A load transient. Initially, the loop is in
regulation and the DC current in the output capacitor is
zero. Suddenly, an extra 4A start flowing out of the output
capacitor while the inductor is still supplying only 1A. This
sudden change will generate a (4A)(R
ESR
) voltage step at
the output; with a typical 0.015
output capacitor ESR,
this is a 60mV step at the output, or 4% (for a 1.5V output
voltage.)
Very quickly, the feedback loop will realize that something
has changed and will move at the bandwidth allowed by
the external compensation network towards a new duty
cycle. If the bandwidth is set to 50kHz, the COMP pin will
get to 60% of the way to 90% duty cycle in 3
μ
s. Now the
inductor is seeing 3.5V across itself for a large portion of
the cycle, and its current will increase from 1A at a rate set
by di/dt = V/L. If the inductor value is 0.5
μ
H, the di/dt will
be 3.5V/0.5
μ
H or 7A/
μ
s. Sometime in the next few micro-
seconds after the switch cycle begins, the inductor current
will have risen to the 5A level of the load current and the
output voltage will stop dropping. At this point, the induc-
tor current will rise somewhat above the level of the output
current to replenish the charge lost from the output
capacitor during the load transient. During the next couple
of cycles, the MIN comparator may trip on and off,
preventing the output from falling below its –5% thresh-
old until the time constant of the compensation loop runs
out and the main feedback amplifier regains control. With
a properly compensated loop, the entire recovery time will
be inside of 10
μ
s.
Most loads care only about the maximum deviation from
ideal, which occurs somewhere in the first two cycles after
the load step hits. During this time, the output capacitor
does all the work until the inductor and control loop regain
control. The initial drop (or rise if the load steps down) is
entirely controlled by the ESR of the capacitor and amounts
to most of the total voltage drop. To minimize this drop,
reduce the ESR as much as possible by choosing low ESR
capacitors and/or paralleling multiple capacitors at the
output. The capacitance value accounts for the rest of the
voltage drop until the inductor current rises. With most
output capacitors, several devices paralleled to get the
ESR down will have so much capacitance that this drop
term is negligible. Ceramic capacitors are an exception; a
small ceramic capacitor can have suitably low ESR with
relatively small values of capacitance, making this second
drop term significant.
Optimizing Loop Compensation
Loop compensation has a fundamental impact on tran-
sient recovery time, the time it takes the LTC1704 to
recover after the output voltage has dropped due to output
capacitor ESR. Optimizing loop compensation entails
maintaining the highest possible loop bandwidth while
ensuring loop stability. The Feedback Component Selec-
tion section describes in detail the techniques used to
design an optimized Type 3 feedback loop, appropriate for
most LTC1704 systems.
Measurement Techniques
Measuring transient response presents a challenge in two
respects: obtaining an accurate measurement and gener-
ating a suitable transient to use to test the circuit. Output
measurements should be taken with a scope probe di-
rectly across the output capacitor. Proper high frequency
probing techniques should be used. In particular, don’t
use the 6" ground lead that comes with the probe! Use an
adapter that fits on the tip of the probe and has a short
ground clip to ensure that inductance in the ground path
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1704B | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
| LTC1705 | Dual 550kHz Synchronous Switching Regulator Controller with 5-Bit VID and 150mA LDO |
| LTC1705EGN | Dual 550kHz Synchronous Switching Regulator Controller with 5-Bit VID and 150mA LDO |
| LTC1710 | Synchronous 8-Bit Up/Down Binary Counters 24-PDIP 0 to 70 |
| LTC1710C | Synchronous 8-Bit Up/Down Binary Counters 24-PDIP 0 to 70 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1704BEGN | 功能描述:IC REG DL BUCK/LINEAR 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| LTC1704BEGN#PBF | 功能描述:IC REG DL BUCK/LINEAR 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| LTC1704BEGN#TR | 功能描述:IC REG DL BUCK/LINEAR 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| LTC1704BEGN#TRPBF | 功能描述:IC REG DL BUCK/LINEAR 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| LTC1704EGN | 功能描述:IC REG DL BUCK/LINEAR 16SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。