参数资料
| 型号： | SC811ULTRT |
| 厂商： | Semtech |
| 文件页数： | 21/23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)
For USB low power mode charging, the external transistor
is turned off. The transistor is turned on when high power
mode is desired. The effect of the switched parallel IPUSB
resistor is to reduce the effective programming resistance
and thus raise the fast-charge current.
An open-drain GPIO can be used directly to engage the
parallel resistor R IPUSB_HI . Care must be taken to ensure that
the R DS-ON of the GPIO is considered in the selection of
R IPUSB_HI . Also important is the part-to-part and tempera-
ture variation of the GPIO R DS-ON , and their contribution to
the USB High Power charge current tolerance. Note also
that IPUSB will be pulled up briefly to as high as 3V during
startup to check for an IPUSB static pinshort to ground. A
small amount of current could, potentially, flow from
IPUSB into the GPIO ESD structure through R IPUSB_HI during
this event. While unlikely to do any harm, this effect must
also be considered.
The 300mAh battery example can be used to illustrate
how this system works. The adapter mode and USB high
power mode fast-charge currents should both be set to
300mA max. The USB input low power fast-charge current
is 100mA max. Refer to the circuit in Figure 5 and the data
of Figures 1a and 1b. For I FQ_AD = 300mA max, use R IPRGM =
7.50kΩ. A fixed IPUSB resistor of R IPUSB = 23.2kΩ programs
I FQ_USB = 100mA max for USB low power charging. When a
parallel resistor R IPUSB_HI = 11.0kΩ resistor is switched in, the
equivalent IPUSB resistor is 7.50kΩ, for I FQ_USB = 300mA
max.
USB Low Power Mode Alternative
Where a USB mode selection signal is not available, or for
a low capacity battery where system cost or board space
make USB low power mode external current program-
ming impractical, USB low power charging can be
supported indirectly. The IPUSB pin resistance can be
selected to obtain the desired USB high power charge
current. Then, with the MODE pin always configured for
USB high power mode, the UVLR feature will ensure that
the charging load on the VIN pin will never pull the USB
Vbus supply voltage below V UVLR regardless of the host or
hub supply limit. The UVLR limit voltage guarantees that
the voltage of the USB Vbus supply will not be loaded
below the low power voltage specification limit, as seen
by any other low power devices connected to the same
USB host or hub.
Independent Programming of Termination
Current
The USB high power mode fast-charge current is limited
to 1000mA, twice the USB high power load limit, and so
this mode may also be used for general purpose adapter
charging. The IPRGM pin resistance to ground determines
the USB high power mode pre-charge current, and the
termination threshold current for all modes. If adapter
mode will not be used in the application, R IPRGM can be
selected to program only the termination threshold
current independently of the fast-charge current, which is
programmed with R IPUSB .
Note that USB high power mode invokes Under-Voltage
Load Regulation, so if charging with an adapter in current
limit, the input voltage can be pulled down no lower than
V UVLR .
USB-only Charging of Very Large Batteries
The SC811/3 can support the charging of very large capac-
ity batteries as high as 2Ah using a USB-only charging
source. The IPRGM resistance lower limit of 2.05kΩ is
intended to limit the fast-charge current while charging in
adapter mode to less than 1A. If only USB charging modes
will be used, then the IPRGM resistor can be chosen as low
as 1kΩ. This extended programming range allows setting
the USB high power mode pre-charge current as high as
400mA (still below the USB specification limit), and the
charge termination current as high as 200mA. (Both of
these currents are determined by R IPRGM .) Note that with
R IPRGM < 2.05kΩ, adapter mode should not be used, as this
can result in potentially destructive fast-charge current.
The USB high power and USB low power fast-charge cur-
rents and the USB low power pre-charge current are
determined by the resistance between IPUSB and GND to
comply with USB specified current limits, and so are unaf-
fected by the IPRGM resistor. Termination detection
requires that the charger be in CV regulation. If the
IPRGM-determined termination threshold current is set
higher than the USB low power mode fast-charge current,
for example, then charge termination will occur the instant
that the battery voltage rises to V CV . Thus USB low power
charging will behave as if trickle-charging until fully
charged, a perfectly safe and acceptable, although slow,
charging scenario.
? 2008 Semtech Corporation
21
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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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