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參數(shù)資料
| 型號： | LT1507CN8-3.3 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Octal D-Type Edge-Triggered Flip-Flops With 3-State Outputs 24-SOIC 0 to 70 |
| 中文描述： | 3 A SWITCHING REGULATOR, 570 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | 0.300 INCH, PLASTIC, DIP-8 |
| 文件頁數(shù)： | 17/20頁 |
| 文件大?。?/td> | 343K |
| 代理商： | LT1507CN8-3.3 |
17
LT1507
APPLICATIO
S I
FOR
ATIO
U
works by prematurely tripping the oscillator before it
reaches its normal peak value. For instance, if the oscilla-
tor is synchronized at twice its nominal frequency, oscil-
lator amplitude will drop by half. A ramp which previously
started at the 40% point now starts at the 80% point! This
effectively blocks slope compensation and the regulator
may respond with fluctuating pulse widths, a “phase
oscillation” if you will. The regulator output stays in
regulation but subharmonic frequencies are generated at
the switch node.
The solution to this problem is to generate an external
ramp that replaces the missing internal ramp. As it turns
out, this is not difficult if the sync signal can be arranged
to have a fairly low duty cycle (< 35%). The ramp is created
by AC coupling a resistor from the sync signal to the
compensation capacitor as shown in Figure 7. This gener-
ates a negative ramp on the V
C
pin during switch ON time
that emulates the missing internally generated ramp.
Amplitude of the ramp should be about 100mV to 200mV
peak-to-peak. The formulas for calculating the values of
R
S
and C
S
are shown below. Note that the C
S
value is
unimportant as long as it exceeds the value given. The
formula assures that the impedance of C
S
will be small
compared to R
S
.
W
U
U
For V
IN
= 4.7, V
OUT
= 3.3V, f = 1MHz, L = 5
μ
H and DC
S
= 25%:
V
mV
P-P
≥
6
=
( .
4 7 1 0 25
6
)
2 1 10
5 10
1 8
71
To avoid small values of R
S
, the compensation capacitor (C
C
)
should be made as small as possible. 2000pF will work in
most situations. If we increase V
PP
to 90mV for a little
cushion, R
S
will be:
R
k
C
pF
S
=
(
)
(
)
=
≥
(
)
(
)
=
5 0 25 0 75
)( .
9
)
.
.
0 09 2 10
110
5 2
20
6
2 1 10
π
5200
612
6
THERMAL CALCULATIONS
Power dissipation in the LT1507 chip comes from four
sources: switch DC loss, switch AC loss, boost circuit
current and input quiescent current. The formulas below
show how to calculate each of these losses. These formu-
las assume continuous mode operation, so they should
not be used for calculating efficiency at light load currents.
Switch loss:
P
R
V
V
nsI
V
f
SW
SW OUT
OUT
IN
OUT
IN
=
+
) (
)
(
)(
)( )
16
Boost current loss:
P
V
V
I
BOOST
OUT
IN
OUT
75
=
+
2
0 008
.
Quiescent current loss:
P
V
V
Q
IN
OUT
=
+
0 003
)
0 005
)
R
SW
= Switch resistance (
≈
0.4
)
16ns = Equivalent switch current/voltage overlap time
f = Switching frequency
R
V
DC
DC
V
C
f
C
( )(
π
S
SYNC
S
S
C
S
S
=
>
(
)(
)
(
)( )
)
1
20
2
P-P
V
SYNC
= Peak-to-peak value of sync signal
DC
S
= Duty cycle of incoming sync signal
V
P-P
= Desired amplitude of ramp
f = Sync frequency
Theoretical minimum amplitude for the ramp, assuming
no internal ramp, is:
V
V
V
DC
)
( )( )(
2
OUT
IN
S
mP
P-P
≥
(
)(
)
2
1
g
mP
= Transconductance from V
C
pin to switch current
(1.8A/V for the LT1507).
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1507CS8 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1507CS8-3.3 | Octal D-Type Edge-Triggered Flip-Flops With 3-State Outputs 24-SO 0 to 70 |
| LT1507I | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1507IN8-3.3 | PTB 21C 21#16 PIN/SKT RECP |
| LT1507IS8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1507CS8 | 功能描述:IC REG BUCK ADJ 1.5A 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:- 設(shè)計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT1507CS8#PBF | 功能描述:IC REG BUCK ADJ 1.5A 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:- 標準包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LT1507CS8#TR | 功能描述:IC REG BUCK ADJ 1.5A 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:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LT1507CS8#TRPBF | 功能描述:IC REG BUCK ADJ 1.5A 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:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LT1507CS8-3.3 | 功能描述:IC REG BUCK 3.3V 1.5A 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:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
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