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參數(shù)資料
| 型號： | LTC3714EG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Intel Compatible, Wide Operating Range, Step-Down Controller with Internal Op Amp |
| 中文描述： | 2 A SWITCHING CONTROLLER, PDSO28 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-28 |
| 文件頁數(shù)： | 20/28頁 |
| 文件大?。?/td> | 345K |
| 代理商： | LTC3714EG |
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LTC3714
20
3714f
APPLICATIOU
Efficiency Considerations
The percent efficiency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the efficiency and which change would
produce the most improvement. Although all dissipative
elements in the circuit produce losses, four main sources
account for most of the losses in LTC3714 circuits:
1. DC I
2
R losses. These arise from the resistances of the
MOSFETs, inductor and PC board traces and cause the
efficiency to drop at high output currents. In continuous
mode the average output current flows through L, but is
chopped between the top and bottom MOSFETs. If the two
MOSFETs have approximately the same R
DS(ON)
, then the
resistance of one MOSFET can simply be summed with the
resistances of L and the board traces to obtain the DC I
2
R
loss. For example, if R
DS(ON)
= 0.01
and R
L
= 0.005
, the
loss will range from 15mW up to 1.5W as the output
current varies from 1A to 10A for a 1.5V output.
2. Transition loss. This loss arises from the brief amount
of time the top MOSFET spends in the saturated region
during switch node transitions. It depends upon the input
voltage, load current, driver strength and MOSFET capaci-
tance, among other factors. The loss is significant at input
voltages above 20V and can be estimated from:
Transition Loss
(1.7A
–1
) V
IN2
I
OUT
C
RSS
f
3. INTV
CC
current. This is the sum of the MOSFET driver
and control currents. This loss can be reduced by supply-
ing INTV
CC
current through the EXTV
CC
pin from a high
efficiency source, such as an output derived boost net-
work or alternate supply if available.
4. C
IN
loss. The input capacitor has the difficult job of
filtering the large RMS input current to the regulator. It
must have a very low ESR to minimize the AC I
2
R loss and
sufficient capacitance to prevent the RMS current from
causing additional upstream losses in fuses or batteries.
Other losses, including C
OUT
ESR loss, Schottky diode D1
conduction loss during dead time and inductor core loss
generally account for less than 2% additional loss.
W
U
U
When making any adjustments to improve efficiency, the
final arbiter is the total input current for the regulator at
your operating point. If you make a change and the input
current decreases, then you improved the efficiency. If
there is no change in input current, then there is no change
in efficiency.
Checking Transient Response
The regulator loop response can be checked by looking at
the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, V
OUT
immediately shifts by an amount
equal to
I
LOAD
(ESR), where ESR is the effective series
resistance of C
OUT
.
I
LOAD
also begins to charge or
discharge C
OUT
generating a feedback error signal used by
the regulator to return V
OUT
to its steady-state value.
During this recovery time, V
OUT
can be monitored for
overshoot or ringing that would indicate a stability prob-
lem. The I
TH
pin external components shown in Figure 8
will provide adequate compensation for most applica-
tions. For a detailed explanation of switching control loop
theory see Linear Technology Application Note 76.
Design Example
As a design example, take a supply with the following
specifications: V
IN
= 7V to 24V (15V nominal),
V
OUT
= 1.15V
±
100mV, I
OUT(MAX)
= 15A, f = 300kHz. First,
calculate the timing resistor with V
ON
= V
OUT
:
R
kHz
pF
k
ON
=
(
)(
)
=
1
300
10
330
and choose the inductor for about 40% ripple current at
the maximum V
IN
:
L
V
.
kHz
A
V
V
H
=
(
)(
)
=
μ
1 15
.
300
0 4 15
1
1 15
24
0 6
.
.
Choosing a standard value of 0.68
μ
H results in a maxi-
mum ripple current of:
=
(
)
μ
(
)
=
I
V
0 68
.
kHz
H
V
V
A
L
1.
300
1
1 15
24
5 4
.
–
.
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| LTC3714EG#PBF | 功能描述:IC STP-DWN CNTRLR W/OPAMP 28SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:2,000 系列:- 應(yīng)用:控制器，DSP 輸入電壓:4.5 V ~ 25 V 輸出數(shù):2 輸出電壓:最低可調(diào)至 1.2V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:30-TFSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:30-TSSOP 包裝:帶卷 (TR) |
| LTC3714EG#PBF | 制造商:Linear Technology 功能描述:DC/DC CONVERTER IC |
| LTC3714EG#TR | 功能描述:IC STP-DWN CNTRLR W/OPAMP 28SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3714EG#TRPBF | 功能描述:IC STP-DWN CNTRLR W/OPAMP 28SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3716EG | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
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