- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄364699 > APPNOTE36 Electroluminescent Display Drivers PDF資料下載
參數(shù)資料
| 型號： | APPNOTE36 |
| 英文描述： | Electroluminescent Display Drivers |
| 中文描述： | 電致發(fā)光顯示驅(qū)動器 |
| 文件頁數(shù)： | 3/12頁 |
| 文件大?。?/td> | 125K |
| 代理商： | APPNOTE36 |
October 1998
3
Application Note 17
Application Note 17
Micrel
Bulk capacitance of at least 120
μ
F per hub is required. This
bulk capacitance provides the short-term transient current
needed during a hot-attachment event. A four-port hub with
a 33
μ
F, 16V tantalum capacitor mounted close to each
downstream connector (see Figures 5, 6, 7, and 8) should
have hot-plug droop much less than 330mV. If electrolytic
capacitors are substituted, 100
μ
F, 10V units should provide
similar transient droop protection.
Figure 3 shows the waveforms for a typical hot-plug event
using the circuit of Figure 6. The hub output capacitor
supplies the bulk of the inrush current to the downstream unit
load (44
, 10
μ
F). This current exceeds 2A for less than 10
μ
s.
The adjacent port voltage droop of 142mV is well within the
330mV specification limit.
100mA steady load
TIME (10
μ
s/div.)
I
O
(
5
V
B
(
1
142mV
330mV
droop
specification
limit
2.57A peak
Figure 3. Typical Hot-Plug Event
Detach Transient Surge
When current in a wire is interrupted, the inductance of the
wire may cause a voltage spike as the magnetic field col-
lapses. To reduce these spikes, which generate EMI, and to
prevent damage to components, 0.01
μ
F, 25V ceramic by-
pass capacitors should be installed directly from V
BUS
pin to
the ground pin at each port.
Printed Circuit Layout
The power circuitry of USB printed circuit boards requires a
customized layout to maximize thermal dissipation and to
minimize voltage drop and EMI.
Printed circuit power and ground traces should be wider than
traces used in a normal digital layout to reduce their in-circuit
resistance. Each solder or header connection may be ex-
pected to contribute up to 10m
, emphasizing the impor-
tance of trace resistance reduction. Table 2 shows typical
resistance in m
/inch for standard conductor widths and
thickness.
Through-hole viaconnections may each have 15m
resis-
tance. If a power trace traverses through a board, use
multiple vias to reduce the interconnect resistance. Placing
traces on both sides of the board, connected with multiple
vias, can cut the trace resistance in half. Solder plating on the
solder-side also reduces trace resistance.
Short and wide same-side traces generally reduce voltage
drop. Ground planes should have a separation line between
output ports to isolate transient droop during hot-attachment.
Ground planes are good thermal radiators and provide EMI
suppression.
Conductor
Thickness
Conductor
Width (inches)
Resistance
(m
/inch)
39.3
19.7
9.8
4.9
1
2
oz/ft
2
0.025
0.050
0.100
0.200
1 oz/ft
2
0.025
0.050
0.100
0.200
19.7
9.8
4.9
2.5
2 oz/ft
2
0.025
0.050
0.100
0.200
9.8
4.9
2.5
1.2
3 oz/ft
2
0.025
0.050
0.100
6.5
3.2
1.6
Table 2. Trace Resistance
Figure 2 shows the various voltage drops for a self-powered
hub caused by printed circuit trace resistance, solder joints,
power switches, and ferrite beads on power and ground
leads. Traces which carry the combined current from the
input should be made heavier to minimize voltage drops, or
separate wide traces should be laid out directly from the input
filter capacitor to each switch input pin.
Voltage Drop Analysis
Adding the drops to the minimum output voltage of 4.75V
shows that a minimum input of 4.85V is needed to ensure
adequate output. The overall voltage drop to each port,
caused by the printed circuit board and overcurrent protec-
tion device, is recommended to be less than 100mV. Ground
traces are as important as power traces, as all voltage drops
are in series. The voltage drop across a self-powered hub
board has three components: board (V
PC
), protection (V
P
),
and output filter (V
FB
).
V
PC
is the trace resistance of the power and ground paths,
approximately 15m
each, times 0.5A.
V
PC
= 2
×
0.015
×
0.5A = 15mV
V
FB
is the resistance of two ferrite beads and their solder
joints, approximately 15m
each
×
0.5A
V
FB
= 2
×
0.015
×
0.5A = 15mV
V
PC
+ V
FB
= 15mV + 15mV = 30mV
The maximum voltage drop recommended across a self-
powered hub is 100mV, so the loss in the protection device
(V
P
) should not exceed 70mV:
V
P
=100mV – 30mV = 70mV
At an output port current of 500mA, the per-port protection
device’s resistance may be up to 140m
:
V
P
= 140m
×
0.5A = 70mV
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| APRX178L | PHOTOLINK Optical TX/RX Modules |
| APRX178LT | PHOTOLINK Optical TX/RX Modules |
| APSC56-21 | SURFACE MOUNT DISPLAY |
| APSC56-21YWW | SURFACE MOUNT DISPLAY |
| APT-104 | Radial-leaded Metal Oxide Varistor ( ROV ); ROV14E331K-2 ( Raychem ) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| APPNOTESMP9100 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Understanding the Power Rating of Caddock MP9100 Resistors |
| APP-NPA1006-CT | 制造商:Nitronex 功能描述:RF & MW AMPLIFIER EVALUATION BOARD/DESIGNER KIT |
| APP-NPT25015-UNTUNED | 制造商:Nitronex 功能描述:RF TRANSISTOR EVALUATION BOARD |
| APP-NPT25100-UNTUNED | 制造商:Nitronex 功能描述:RF TRANSISTOR EVALUATION BOARD |
| APP-NPT35050A-UNTUNED | 制造商:Nitronex 功能描述:RF TRANSISTOR EVALUATION BOARD |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。