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參數(shù)資料
| 型號： | LTC1267CG-ADJ5 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Circular Connector; No. of Contacts:37; Series:LJT06R; Body Material:Aluminum; Connecting Termination:Crimp; Connector Shell Size:15; Circular Contact Gender:Socket; Circular Shell Style:Straight Plug; Insert Arrangement:15-35 |
| 中文描述： | 0.05 A DUAL SWITCHING CONTROLLER, 400 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | PLASTIC, SSOP-28 |
| 文件頁數(shù)： | 7/16頁 |
| 文件大?。?/td> | 341K |
| 代理商： | LTC1267CG-ADJ5 |
7
LTC1267
LTC1267-ADJ/LTC1267-ADJ5
OPERATIOU
The LTC1267 series consists of two individual regulator
blocks, each using current mode, constant off-time archi-
tectures to synchronously switch an external pair of
complementary power MOSFETs. The two regulators are
internally set to provide output voltages of 3.3V and 5V for
the LTC1267. The LTC1267-ADJ is configured to provide
two adjustable output voltages, each set by their indi-
vidual external resistor dividers. The LTC1267-ADJ5 has
adjustable and 5V output voltages. Operating frequency is
individually set on each section by the external capacitors
attached to the C
T
pin.
The output voltage is sensed by an internal voltage divider
connected to the Sense
–
pin or external divider returned
to the V
FB
pin (LTC1267-ADJ, LTC1267-ADJ5). A voltage
comparator V and a gain block G compare the divided
output voltage with a reference voltage of 1.25V. To
optimize efficiency, the LTC1267 series automatically
switches between two modes of operation, Burst Mode
and continuous mode. The voltage comparator is the
primary control element when the device is in Burst Mode
operation, while the gain block controls the output voltage
in continuous mode.
A low dropout 4.5V regulator provides the operating
voltage V
CC
for the MOSFET drivers and control circuitry
during start-up. During normal operation, the LTC1267
family powers the drivers and control from the output via
the EXT V
CC
pin to improve efficency. The NGate pin is
referenced to ground and drives the N-channel MOSFET
gate directly. The P-channel gate drive must be referenced
to the main supply input V
IN
, which is accomplished by
level-shifting the PDrive signal via an internal 550k resis-
tor and an external capacitor.
During the switch “ON” cycle in continuous mode, current
comparator C monitors the voltage between Sense
+
and
Sense
–
pins connected across an external shunt in series
with the inductor. When the voltage across the shunt
reaches its threshold value, the PGate output is switched
to V
IN
, turning off the P-channel MOSFET. The timing
capacitor C
T
is now allowed to discharge at a rate deter-
mined by the off-time controller. The discharge current is
made proportional to the output voltage to model the
inductor current, which decays at a rate that is also
(Refer to Functional Diagram)
proportional to the output voltage. While the timing ca-
pacitor is discharging, the NGate output is high, turning
on the N-channel MOSFET.
When the voltage on the timing capacitor has discharged
past V
TH1
, comparator T trips, setting the flip-flop. This
causes the NGate output to go low (turning off the
N-channel MOSFET) and the PGate output to also go low
(turning the P-channel MOSFET back on). The cycle then
repeats. As the load current increases, the output voltage
decreases slightly. This causes the output of the gain
stage to increase the current comparator threshold, thus
tracking the load current.
The sequence of events for Burst Mode
operation is very
similar to continuous operation with the cycle interrupted
by the voltage comparator. When the output voltage is at
or above the desired regulated value, the P-channel
MOSFET is held off by comparator V and the timing
capacitor continues to discharge below V
TH1
. When the
timing capacitor discharges past V
TH2
, voltage compara-
tor S trips, causing the internal SLEEP line to go low and
the N-channel MOSFET to turn off.
The circuit now enters sleep mode with both power
MOSFETs turned off. In sleep mode a majority of the
circuitry is turned off, dropping the quiescent current
from several mA (with the MOSFETs switching) to 360
μ
A.
The load current is now being supplied by the output
capacitor. When the output voltage has dropped by the
amount of hysteresis in comparator V, the P-channel
MOSFET is again turned on and this process repeats.
To avoid the operation of the current loop interfering with
Burst Mode
operation, a built-in offset V
OS
is incorporated
in the gain stage. This prevents the current comparator
threshold from increasing until the output voltage has
dropped below a minimum threshold.
To prevent both the external MOSFETs from ever being
turned on at the same time, feedback is incorporated to
sense the state of the driver output pins. Before the
NGate output can go high, the PDrive output must also be
high. Likewise, the PDrive output is prevented from going
low while the NGate output is high.
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| LTC1272-3ACN | 功能描述:IC A/D CONV 12BIT SAMPLING 24DIP RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1,000 系列:- 位數(shù):12 采樣率（每秒）:300k 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:75mW 電壓電源:單電源 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:24-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:24-SOIC 包裝:帶卷 (TR) 輸入數(shù)目和類型:1 個(gè)單端，單極；1 個(gè)單端，雙極 |
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| LTC1272-3ACSW | 功能描述:IC A/D CONV 12BIT SAMPLNG 24SOIC RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 其它有關(guān)文件:TSA1204 View All Specifications 標(biāo)準(zhǔn)包裝:1 系列:- 位數(shù):12 采樣率（每秒）:20M 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:2 功率耗散（最大）:155mW 電壓電源:模擬和數(shù)字 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-TQFP 供應(yīng)商設(shè)備封裝:48-TQFP（7x7） 包裝:Digi-Reel® 輸入數(shù)目和類型:4 個(gè)單端，單極；2 個(gè)差分，單極 產(chǎn)品目錄頁面:1156 (CN2011-ZH PDF) 其它名稱:497-5435-6 |
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| LTC1272-3ACSW#TR | 功能描述:IC ADC 12BIT SAMPLING 24SOIC RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1,000 系列:- 位數(shù):12 采樣率（每秒）:300k 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:75mW 電壓電源:單電源 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:24-SOIC（0.295"，7.50mm 寬） 供應(yīng)商設(shè)備封裝:24-SOIC 包裝:帶卷 (TR) 輸入數(shù)目和類型:1 個(gè)單端，單極；1 個(gè)單端，雙極 |
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