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参数资料
| 型号： | GM3255S8R |
| 厂商： | American Power Management Inc. |
| 元件分类： | DC/DC变换器 |
| 英文描述： | 1.5A 280kHz DC-DC CONVERTOR BOOST REGULATOR |
| 中文描述： | 1.5A的为280kHz的DC - DC转换器升压稳压器 |
| 文件页数： | 5/19页 |
| 文件大小： | 234K |
| 代理商： | GM3255S8R |
Where
I
= the current through the switch;
SW
D = the duty cycle or percentage of switch on-time.
I
and D are dependent on the type of converter. In
SW
a boost convert,
In a flyback converter,
The switch saturation voltage, V
, is the last ma-
(CE)SAT
jor source of on-chip power loss. V
is the collec-
(CE)SAT
tor-emitter voltage of the internal NPN transistor when
it is driven into saturation by its base drive current. The
value for V
can be obtained from the specifica-
(CE)SAT
tions or from the graphs, as "Switch Saturation
Voltage." Thus,
Finally, the total on-chip power losses are
Power dissipation in a semiconductor device results in
the generation of heat in the junctions at the surface of
the chip. This heat is transferred to the surface of the
IC package, but a thermal gradient exists due to the re-
sistive properties of the package molding compound.
The magnitude of the thermal gradient is expressed in
manufacturers' data sheets as Q , or junction-to- ambi-
JA
ent thermal resistance. The on-chip junction tempera-
ture can be calculated if Q , the air temperature near
JA
the surface of the IC, and the on-chip power dissipation
are known.
T = T + (P Q )
JA
D JA
where:
T = IC or FET junction temperature (°C);
J
T = ambient temperature (°C);
A
P = power dissipated by part in question(W);
D
Q
= junction-to ambient thermal resistance (°C / W).
JA
For GM3255,
Q
= 165°C / W. Once the designer
JA
has calculated T , the question of whether the GM3255
J
can be used in an application is settled. If T exceeds
J
150°C, the absolute maximum allowable junction tem-
perature, the GM3255 is not suitable for that applica-
tion.
I
@ I
X D X
SW(AVG)
LOAD
1
Efficiency
D @
V
-V
OUT
IN
V
OUT
I
@
X
SW(AVG)
1
Efficiency
V
I
OUT LOAD
V
IN
D @
V
OUT
V
+
V
OUT
IN
NS
NP
P
@ VI
X D
SAT
(CE)SAT SW
P
= P
+ P
D
BIAS
DRIVER
SAT
If T
approaches 150°C, the designer should con-
J
sider possible means of reducing the junction temper-
ature. Perhaps another converter topology could be
selected to reduce the switch current. Increasing the
airflow across the surface of the chip might be consid-
ered to reduce T .
A
Output Setting
GM3255 develops a 1.276 V reference (V
) from
REF
the FB pin to ground. Output voltage is set by con-
necting the FB pin to an output resistor divider (Figure
16). The FB pin bias current represents a small error
and can usually be ignored for values of R2 up to 7k.
The suggested value for R2 is 6.19k.
Circuit Layout Guidelines
In any switching power supply, circuit layout is very
important for proper operation. Rapidly switching cur-
rents combined with trace inductance generates volt-
age transitions that can cause problems. Therefore
the following guidelines should be followed in the lay-
out.
1. In boost circuits, high AC current circulates within
the loop composed of the diode, output capacitor, and
on-chip power transistor. The length of associated
traces and leads should be kept as short as possible.
In the flyback circuit, high AC current loops exist on
both sides of the transformer. On the primary side,
the loop consists of the input capacitor, transformer,
and on-chip power transistor, while the transformer,
rectifier diodes, and output capacitors form another
loop on the secondary side. Just as in the boost cir-
cuit, all traces and leads containing large AC current
should be kept short.
2. Separate the low current signal grounds from the
power grounds. Use single point grounding or ground
plane construction for the best results.
3. Locate the voltage feedback as near the IC as, pos-
sible to keep the sensitive feedback wiring short.
Connect feedback resistors to the low current analog
ground.
G
M
3
2
5
13
VOUT
VREF
FB
PIN
R1
R2
V=
OUT
V
(1 +
)
REF
R1
R2
R1 = R2 (
-1)
VOUT
1.276
Figure 16. Output Resistor Divider
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相关代理商/技术参数 |
参数描述 |
|---|---|
| GM3255S8T | 制造商:GAMMA 制造商全称:GAMMA 功能描述:1.5A 280kHz DC-DC CONVERTOR BOOST REGULATOR |
| GM330K | 制造商:Mallory Sonalert Products Inc 功能描述:Cap Ceramic 33pF 500V SL 10% (6 X 4mm) Radial 6.4mm 85°C 制造商:CORNELL DUBILIER ELECTRONICS 功能描述:Cap Ceramic 33pF 500V SL 10% (6 X 4mm) Radial 6.4mm 85°C |
| GM331K | 功能描述:瓷片电容器 500V 330pF DISC RoHS:否 制造商:Vishay/Cera-Mite 电容:0.01 uF 容差:20 % 电压额定值:3 kV 工作温度范围:- 25 C to + 105 C 损耗因数 DF: 端接类型:Radial 产品:High Voltage Ceramic Disc Capacitors |
| GM3326 | 制造商:GAMMA 制造商全称:GAMMA 功能描述:PWM,PWM/PFM SWITCHING STEP-UP & DOWN DC/DC CONVERTER CONTROLLER ICS |
| GM3326-2.5ST25R | 制造商:GAMMA 制造商全称:GAMMA 功能描述:PWM,PWM/PFM SWITCHING STEP-UP & DOWN DC/DC CONVERTER CONTROLLER ICS |
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