參數(shù)資料
型號(hào)： LTC1266CS-3.3
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： Synchronous Regulator Controller for N- or P-Channel MOSFETs
中文描述： SWITCHING CONTROLLER, 400 kHz SWITCHING FREQ-MAX, PDSO16
封裝： 0.150 INCH, PLASTIC, SO-16
文件頁(yè)數(shù)： 14/20頁(yè)
文件大?。?/td> 361K
代理商： LTC1266CS-3.3
14
LTC1266
LTC1266-3.3/LTC1266-5
APPLICATIU
discharge C
OUT
until the regulator loop adapts to the
current change and returns V
OUT
to its steady-state value.
During this recovery time V
OUT
can be monitored for
overshoot or ringing which would indicate a stability
problem. The Pin 7 external components shown in the
Figure 1 circuit will prove adequate compensation for
most applications.
W
U
U
power MOSFET is 15nC. This results in I
GATECHG
= 6mA
in 200kHz continuous operation for a 2% to 3% typical
mid-current loss with V
IN
= 5V.
Note that the gate charge loss increases directly with
both input voltage and operating frequency. This is the
principal reason why the highest efficiency circuits
operate at moderate frequencies. Furthermore, it ar-
gues against using larger MOSFETs than necessary to
control I
2
R losses, since overkill can cost efficiency as
well as money!
3. I
2
R losses are easily predicted from the DC resistances
of the MOSFET, inductor and current shunt. In continu-
ous mode the average output current flows through L
and R
SENSE
, but is “chopped” between the topside and
bottom-side MOSFETs. If the two MOSFETs have ap-
proximately the same R
DS(ON)
, then the resistance of
one MOSFET can simply be summed with the resis-
tances of L and R
SENSE
to obtain I
2
R losses. For
example, if each R
DS(ON)
= 0.05
, R
L
= 0.05
and
R
SENSE
= 0.02
, then the total resistance is 0.12
. This
results in losses ranging from 3.5% to 15% as the
output current increases from 1A to 5A. I
2
R losses
cause the efficiency to roll off at high output currents.
Figure 8 shows how the efficiency losses in a typical
LTC1266 series regulator end up being apportioned. The
gate charge loss is responsible for the majority of the
efficiency lost in the mid-current region. If Burst Mode
operation was not employed at low currents, the gate
charge loss alone would cause efficiency to drop to
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. Percent efficiency can be
expressed as:
% Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc., are the individual losses as a percent-
age of input power. (For high efficiency circuits, only small
errors are incurred by expressing losses as a percentage
of output power).
Although all dissipative elements in the circuit produce
losses, three main sources usually account for most of the
losses in LTC1266 series circuits: 1) LTC1266 DC bias
current, 2) MOSFET gate charge current and 3) I
2
R losses.
1. The DC supply current is the current which flows into
V
IN
(Pin 2). For V
IN
= 10V the LTC1266 DC supply
current is 170
μ
A for no load, and increases proportion-
ally with load up to a constant 2.1mA after the LTC1266
series has entered continuous mode. Because the DC
bias current is drawn from V
IN
, the resulting loss
increases with input voltage. For V
IN
= 5V the DC bias
losses are generally less than 1% for load currents over
30mA. However, at very low load currents the DC bias
current accounts for nearly all of the loss.
2. MOSFET gate charge current results from switching the
gate capacitance of the power MOSFETs. Each time a
MOSFET gate is switched from low to high to low again,
a packet of charge dQ moves from Power V
IN
to ground.
The resulting dQ/dt is a current flowing into Power V
IN
(Pin 5) which is typically much larger than the DC
supply current. In continuous mode, I
GATECHG
= f (Q
N
+
Q
P
). The typical gate charge for a 0.05
N-channel
Figure 8. Efficiency Loss
I
OUT
(A)
0.01
E
90
95
1
LTC1266 F08
85
80
0.03
0.1
0.3
5
100
GATE CHARGE
LTC1266 I
Q
I
2
R
相關(guān)PDF資料
PDF描述
LTC1266CS-5 Synchronous Regulator Controller for N- or P-Channel MOSFETs
LTC1267- ADJ 500kHz and 1MHz High Efficiency 1.5A Switching Regulators; Package: SO; No of Pins: 8; Temperature Range: -40?°C to 85?°C
LTC1267- ADJ5 500kHz and 1MHz High Efficiency 1.5A Switching Regulators; Package: SO; No of Pins: 8; Temperature Range: -40?°C to 85?°C
LTC1267-ADJ5 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
LTC1267-ADJ XTAL MTL T/H HC49/US
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1266CS-5 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:否 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC1266CS-5#PBF 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:是 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC1266CS-5#TR 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:否 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC1266CS-5#TRPBF 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:否 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC1266IS 功能描述:IC REG CTRLR BST PWM CM 16-SOIC RoHS:否 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
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