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參數(shù)資料
| 型號(hào)： | LM1949M |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類(lèi)： | 外設(shè)及接口 |
| 英文描述： | LM1949 Injector Drive Controller |
| 中文描述： | 0.022 A BUF OR INV BASED PRPHL DRVR, PDSO8 |
| 封裝： | 0.150 INCH, SO-8 |
| 文件頁(yè)數(shù)： | 7/10頁(yè) |
| 文件大?。?/td> | 214K |
| 代理商： | LM1949M |
POWER DISSIPATION
The power dissipation of the system shown in Figure 1 is
dependent upon several external factors, including the fre-
quency and duty cycle of the input waveform to Pin 1. Cal-
culations are made more difficult since there are many dis-
continuities and breakpoints in the power waveforms of the
various components, most notably at the peak-to-hold tran-
sition. Some generalizations can be made for normal opera-
tion. For example, in a typical cycle of operation, the majori-
ty of dissipation occurs during the hold state. The hold state
is usually much longer than the peak state, and in the peak
state nearly all power is stored as energy in the magnetic
field of the injector, later to be dumped mostly through the
zener. While this assumption is less accurate in the case of
low battery voltage, it nevertheless gives an unexpectedly
accurate set of approximations for general operation.
The following nomenclature refers to Figure 1. Typical val-
ues are given in parentheses:
e
Sense Resistor (0.1
X
)
V
H
e
Sense Input Hold Voltage (.094V)
V
p
e
Sense Input Peak Voltage (.385V)
V
Z
e
Z
1
Zener Breakdown Voltage (33V)
V
BATT
e
Battery Voltage (14V)
L
1
e
Injector Inductance (.002H)
R
1
e
Injector Resistance (1
X
)
n
e
Duty Cycle of Input Voltage of Pin 1 (0 to 1)
f
e
Frequency of Input (10Hz to 200Hz)
Q
1
Power Dissipation:
P
Q
&
n
#
V
BATT
#
V
H
R
S
Zener Dissipation:
(V
P2
a
V
H2
)
((V
Z
-V
BATT
)
#
R
S2
)Watts
Injector Dissipation:
P
I
&
n
#
R
1
#
V
H2
R
S2
Watts
Sense Resistor:
P
R
&
nV
H2
R
S2
Watts
P
R
(worst case)
&
nV
P2
R
S2
Watts
R
S
Watts
P
Z
&
V
Z
#
L
1
#
f
#
SWITCHING INJECTOR DRIVER CIRCUIT
The power dissipation of the system, and especially of Q
1
,
can be reduced by employing a switching injector driver cir-
cuit. Since the injector load is mainly inductive, transistor Q
1
can be rapidly switched on and off in a manner similar to
switching regulators. The solenoid inductance will naturally
integrate the voltage to produce the required injector cur-
rent, while the power consumed by Q
1
will be reduced. A
note of caution: The large amplitude switching voltages that
are present on the injector can and do generate a tremen-
dous amount of radio frequency interference (RFI). Because
of this, switching circuits are not recommended. The extra
cost of shielding can easily exceed the savings of reduced
power. In systems where switching circuits are mandatory,
extensive field testing is required to guarantee that RFI can-
not create problems with engine control or entertainment
equipment within the vicinity.
The LM1949 can be easily modified to function as a switch-
er. Accomplished with the circuit of Figure 7, the only addi-
tional components required are two external resistors, R
A
and R
B
. Additionally, the zener needs to be reconnected, as
shown, to R
S
. The amount of ripple on the hold current is
easily controlled by the resistor ratio of R
A
to R
B
. R
B
is kept
small so that sense input bias current (typically 0.3 mA) has
negligible effect on V
H
. Duty cycle and frequency of oscilla-
tion during the hold state are dependent on the injector
characteristics, R
A
, R
B
, and the zener voltage as shown in
the following equations.
Hold Current
&
V
H
R
S
Minimum Hold Current
&
V
H
b
R
B
R
A
#
V
Z
R
S
Ripple or
D
I Hold
&
R
B
R
A
#
V
Z
#
1
R
S
f
o
&
R
S
P
Q
&
n
#
#
1
b
V
BATT
V
SAT
e
Q
1
Saturation Volt
@
E
1 Amp (1.5V)
P
Z
&
n
#
V
BATT
#
V
H
R
S
P
RA
&
V
B
#
V
Z
R
1
As shown, the power dissipation by Q
1
in this manner is
substantially reduced. Measurements made with a thermo-
couple on the bench indicated better than a fourfold reduc-
tion in power in Q
1
. However, the power dissipation of the
zener (which is independent of the zener voltage chosen) is
increased over the circuit of Figure 1.
L
1
#
R
A
R
B
#
V
BATT
V
Z
V
Z
J
#
V
SAT
#
#
1
b
V
BATT
f
o
e
Hold State Oscillation Frequency
V
Z
J
Duty Cycle of f
o
&
V
BATT
V
Z
Component Power Dissipation
R
S
#
V
H
TL/H/5062–9
FIGURE 6. Switching Waveforms
7
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM1949N | 功能描述:開(kāi)關(guān)變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開(kāi)關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM1949N/NOPB | 功能描述:開(kāi)關(guān)變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開(kāi)關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM1949N/NOPB | 制造商:Texas Instruments 功能描述:Power Driver IC |
| LM194C | 制造商:Texas Instruments 功能描述: |
| LM194H/883 | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:LM194/LM394 Supermatch Pair |
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