參數(shù)資料
型號(hào)： LTC1148HVIS-5
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： SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO14
封裝： 0.150 INCH, PLASTIC, SOP-14
文件頁(yè)數(shù)： 11/20頁(yè)
文件大?。?/td> 250K
代理商： LTC1148HVIS-5
11
LTC1148
LTC1148-3.3/LTC1148-5
114835fd
APPLICATIOU
In surface mount applications multiple capacitors may
have to be paralleled to meet the capacitance, ESR, or
RMS current handling requirements of the application.
Aluminum electrolytic and dry tantalum capacitors are
both available in surface mount configurations. In the
case of tantalum, it is critical that the capacitors are surge
tested for use in switching power supplies. An excellent
choice is the AVX TPS series of surface mount tantalums,
available in case heights ranging from 2mm to 4mm. For
example, if 200
μ
F/10V is called for in an application
requiring 3mm height, two AVX 100
μ
F/10V (P/N TPSD
107K010) could be used. Consult the manufacturer for
other specific recommendations.
At low supply voltages, a minimum capacitance at C
OUT
is needed to prevent an abnormal low frequency oper-
ating mode (see Figure 4). When C
OUT
is made too
small, the output ripple at low frequencies will be large
enough to trip the voltage comparator. This causes
Burst Mode
operation to be activated when the LTC1148
series would normally be in continuous operation. The
effect is most pronounced with low values of R
SENSE
and can be improved by operating at higher frequencies
with lower values of L. The output remains in regulation
at all times.
W
U
U
several cycles to respond to a step in DC (resistive) load
current. When a load step occurs, V
OUT
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
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 6 external components shown in the
Figure 1 circuit will prove adequate compensation for
most applications.
A second, more severe transient is caused by switching in
loads with large (>1
μ
F) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
with C
OUT
, causing a rapid drop in V
OUT
. No regulator can
deliver enough current to prevent this problem if the load
switch resistance is low and it is driven quickly. The only
solution is to limit the rise time of the switch drive so that
the load rise time is limited to approximately 25
C
LOAD
.
Thus a 10
μ
F capacitor would require a 250
μ
s rise time,
limiting the charging current to about 200mA.
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 LTC1148 series circuits: 1) LTC1148 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 3 less the gate charge current. For V
IN
= 10V the
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
(V
IN
– V
OUT
) VOLTAGE (V)
0
C
O
μ
F600
1000
4
LTC1148 F04
400
200
0
1
2
3
5
800
L = 50
μ
H
R
SENSE
= 0.02
L = 25
μ
H
R
SENSE
= 0.02
L = 50
μ
H
R
SENSE
= 0.05
Figure 4. Minimum Value of C
OUT
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LTC1148HVIS-5#PBF 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC RoHS:是 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1148HVIS-5#TR 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1148HVIS-5#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC RoHS:是 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1148L 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Efficiency Synchronous Step-Down Switching Regulators
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