参数资料
| 型号： | SC811ULTRT |
| 厂商： | Semtech |
| 文件页数： | 20/23页 |
| 文件大小： | 0K |
| 描述： | IC BATTERY MANAGEMENT |
| 标准包装： | 1 |
| 系列： | * |
| 其它名称： | SC811ULDKR |
SC811 / SC813
Applications Information (continued)
During charging, a short to ground applied to the active
current programming pin (IPRGM or IPUSB) is detected,
while a short to ground on the inactive programming pin
is ignored. Pin-short detection on an active current pro-
gramming pin forces the SC811/3 into reset, turning off
?
Attaching the part to a larger copper footprint
will enable better heat transfer from the device,
especially on PCBs with internal ground and
power planes.
the output. A pin-short on either programming pin will
prevent startup regardless of the mode selected. When
the IPRGM or IPUSB pin-short condition is removed, the
charger begins normal operation automatically without
input power cycling.
Over-Current Protection
Over-current protection is provided in all modes of opera-
tion, including CV regulation. The output current is limited
to either the programmed pre-charge current limit value
or the fast-charge current limit value, depending on the
voltage at the output.
Design Considerations — Large Battery
A battery with a desired fast-charge current exceeding
500mA is most consistent with the USB fixed 1:5 current
ratio low-to-high power model of operation. For example,
consider an 800mAh battery, with maximum fast-charge
current of 800mA. The adapter input fast-charge should
be configured for 800mA max (R IPRGM = 2.80kΩ). Select
R IPUSB = 4.53k Ω to set USB high power fast-charge to
450mA, and the USB low power fast-charge set to
450/5 = 90mA. The MODE pin tri-level logical input can be
used to select between USB high power and USB low
power modes whenever a fixed 5:1 current ratio is
desired.
Operation Without a Battery
The SC811/3 can be operated as a 4.2V LDO regulator
without the battery present, for example, factory testing.
If this use is anticipated, the output capacitance C BAT
should be at least 2.2μF to ensure stability. To operate the
charger without a battery, the ENB pin must be driven low
or grounded.
Capacitor Selection
Low cost, low ESR ceramic capacitors such as the X5R and
X7R dielectric material types are recommended. The BAT
pin capacitor range is 1μF to 22μF. The VIN pin capacitor
is typically between 0.1 μF and 2.2 μF, although larger
values will not degrade performance. Capacitance must
be evaluated at the expected bias voltage, rather than the
zero-volt capacitance rating.
PCB Layout Considerations
Layout for linear devices is not as critical as for a switching
regulator. However, careful attention to detail will ensure
reliable operation.
Design Considerations — Small Battery
A battery with a desired fast-charge current less than
500mA will not be charged in minimum charge time when
in USB low power mode of operation with a 1:5 low-to-
high power mode current ratio. A 300mAh battery can be
used as an example with maximum fast-charge current of
300mA. In this example, the adapter input and USB input
high power fast-charge currents should both be set to
300mA. The USB low power fast-charge current of, for
example, 90mA, for a low-to-high power current ratio of
1:3.3, would provide a shorter charge time than the 60mA
obtained with the fixed USB low-to-high power charging
current ratio of 1:5.
An arbitrary ratio of USB low-to-high power charging cur-
rents can be obtained using an external n-channel FET
operated with a processor GPIO signal to engage a second
parallel IPUSB resistor, while selecting high power mode
(MODE pin driven high) for both low or high power charg-
ing. The external circuit is illustrated in Figure 5.
?
Place input and output capacitors close to the
IPUSB
5
device for optimal transient response and device
?
behavior.
Connect all ground connections directly to the
ground plane. If there is no ground plane,
USB Hi/Lo
Power Select
R IPUSB_HI
R IPUSB
connect to a common local ground point before
connecting to board ground near the GND pin.
Figure 5. External programming of arbitrary USB high
power and low power charge currents.
? 2008 Semtech Corporation
20
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SC813 | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Adapter/USB Tri-Mode Single-cell Li-ion Charger |
| SC813EVB | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Adapter/USB Tri-Mode Single-cell Li-ion Charger |
| SC813M-PE-FOAM-BUTTON | 制造商:SUPER MICRO COMPUTER, INC. 功能描述:CSE-813MT-300CB FOAM SET BUTTON - Bulk |
| SC813M-PE-FOAM-TOP | 制造商:Supermicro Computer Inc 功能描述:CSE-813MT-300CB FOAM SET TOP - Bulk |
| SC813MT-300C | 制造商:Supermicro Computer Inc 功能描述:1U CHASSIS |
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