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參數(shù)資料
| 型號： | LTC1504CS8 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 1 A SWITCHING REGULATOR, 250 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | 0.150 INCH, PLASTIC, SO-8 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 249K |
| 代理商： | LTC1504CS8 |
6
LTC1504
APPLICATIO
S I
N
FOR
ATIO
U
OVERVIEW
The LTC1504 is a complete synchronous switching regu-
lator controller (see Block Diagram). It includes two
on-chip 1.5
power MOSFETs, eliminating the need for
external power devices and minimizing external parts
count. The internal switches are set up as a synchronous
buck converter with a P-channel device (Q1) from the
input supply to the switching node and an N-channel
device (Q2) as the synchronous rectifier device from the
switching node to ground. An external inductor, input and
output bypass capacitors and the compensation network
complete the control loop. The LTC1504 adjustable output
parts require an additional pair of resistors to set the
output voltage. The LTC1504-3.3 parts include an onboard
resistor divider preset to a 3.3V output voltage. A func-
tional 3.3V output regulator can be constructed with an
LTC1504-3.3 and as few as four external components.
The LTC1504 feedback loop includes a precision reference
trimmed to 1% (V
REF
), a wide bandwidth transconductance
feedback amplifier (FB) and an onboard PWM generator
(SAW and PWM). Two additional feedback comparators
(MIN and MAX) monitor the feedback voltage and override
the primary feedback amplifier when the regulated out falls
outside a
±
3% window, improving transient response.
The internal sawtooth oscillator typically runs at 200kHz.
Q1 and Q2 are capable of carrying peak currents in excess
of 500mA, with the continuous output power level limited
primarily by the thermal dissipation of the SO-8 package.
With a 5V input and a 3.3V output, the LTC1504 can supply
500mA of continuous output current with an appropriate
layout. An on-chip current limit circuit, set with a single
external resistor, can be used to help limit power dissipa-
tion. See the Thermal Considerations section for more
information.
W
U
Theory of Operation
The LTC1504 primary feedback loop consists of the main
error amplifier FB, the PWM generator, the output drive
logic and the power switches. The loop is closed with the
external inductor and the output bypass capacitor. The
feedback amplifier senses the output voltage directly at the
SENSE pin for fixed output versions or through an external
resistor divider in the adjustable output version. This
feedback voltage is compared to the 1.265V internal
reference voltage by FB and an error signal is generated at
the COMP pin. COMP is a high impedance node that is
brought out to an external pin for optimizing the loop
compensation.
COMP is compared to a 200kHz sawtooth wave by com-
parator PWM. This raw pulse-width modulated signal is
logically combined with the outputs of the transient com-
parators MIN and MAX before reaching the output stage.
The output stage generates nonoverlapping drive for the
onboard P- and N-channel power MOSFETs, which drive
the SW pin with a low impedance image of the PWM
waveform. Typical open-loop output impedance at SW is
between 1
and 3
, depending on supply voltage. This
high power pulse train is filtered by the external inductor
and capacitor, providing a steady DC value at the output
node. This node returns to FB or SENSE, closing the loop.
The MIN and MAX comparators in the feedback loop
provide high speed fault correction in situations where the
FB amplifier may not respond quickly enough. MIN com-
pares the feedback signal to a voltage 40mV (3%) below
the internal reference. At this point, MIN overrides the FB
amplifier and forces the loop to full duty cycle. Similarly,
MAX monitors the output voltage at 3% above the internal
reference and forces the output to 0% duty cycle when
tripped. These two comparators prevent extreme output
perturbations with fast output transients, while allowing
the main feedback loop to be optimally compensated for
stability.
The LTC1504 includes yet another feedback loop that
controls operation in current limit. The I
LIM
amplifier
monitors the voltage at the SW pin while Q1 is on. It
compares this voltage to the voltage at the I
MAX
pin. As the
peak current through Q1 rises, the voltage drop across it
due to its R
ON
increases proportionally. When SW drops
below I
MAX
, indicating the current through Q1 has in-
creased beyond the desired value, I
LIM
starts pulling a
controlled amount of current out of SS, the external soft
start pin. As SS falls, it pulls COMP down with it, limiting
the duty cycle and reducing the output voltage to control
the current. The speed at which the current limit circuit
reacts is set by the value of the external soft start capacitor.
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| LTC1504CS8#PBF | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC1504CS8#TR | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC1504CS8#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 0.5A 8SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
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