参数资料
| 型号： | SC811ULTRT |
| 厂商： | Semtech |
| 文件页数： | 19/23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)
straint (along with CC, CV, and CT constraints), but it is
active only when one of the USB modes is selected.
In either of the USB modes, if the VIN voltage is externally
pulled below V UVLR , the UVLR feature will reduce the charg-
ing current to zero. This condition will not be interpreted
as termination and will not result in an end-of-charge indi-
cation. The STATB pin will remain asserted as if charging is
continuing. This behavior prevents repetitive indications
of end-of-charge alternating with start-of-charge in the
case that the external VIN load is removed or is
intermittent.
USB High Power and Low Power Support
The USB specification restricts the load on the USB Vbus
power network to 100mA for low power devices and for
high power devices prior to granting permission for high
power operation. The specification restricts the Vbus load
to 500mA for high power devices after granting permis-
sion to operate as a high power device. A fixed 1:5 ratio of
low power to high power charging current is desirable for
charging batteries with maximum fast-charge current of
at least 500mA. For this application, the SC811/3 provides
fixed 1:5 current ratio low-to-high power mode support,
The OVP threshold of the SC811 has been set relatively
high to permit the use of poorly regulated adapters. Such
adapters may output a high voltage until loaded by the
charger. A too-low OVP threshold could prevent the
charger from ever turning on and loading the adapter to
a lower voltage. If the adapter voltage remains high
despite the charging load, the fast thermal limiting feature
will immediately reduce the charging current to prevent
overheating of the SC811. This behavior is illustrated in
Figure 4, in which V BAT = 3.0V, I FQ = 700mA, and V VIN is
stepped from 0V to 8.1V. Initially, power dissipation in the
SC811 is 3.6W.
V VIN =8.1V, V BAT =3.0V
I BAT =700mA (Initially), P DISSIPATION =3.6W (Initially)
I BAT (100mA/div)
V VIN (2V/div)
V BAT (2V/div)
V VIN ,V BAT =0V—
via the tri-level MODE input pin.
I BAT =0mA—
1s/div
For batteries with maximum fast-charge current less than
500mA, a fixed 1:5 low/high power charge current ratio
will result in suboptimal charging in USB low power mode.
For example, a 250mAh battery will typically require a
fast-charge current of 250mA or less. A fixed 1:5 ratio for
USB low-to-high power charging current will unnecessar-
ily reduce charging current to 50mA, well below the
100mA permitted. In this case, it may be preferable to
program USB low-power fast-charge current by switching
an external programming resistor. See the section Design
Considerations — Small Battery.
Input Over-Voltage Protection
The VIN pin is protected from over-voltage to at least 30V
above GND. When the input voltage exceeds the Over-
Voltage Protection (OVP) rising threshold ( VT OVP-R ),
charging is halted. When the input voltage falls below the
OVP falling threshold (VT OVP-F ), charging restarts. An OVP
fault turns off the STATB output. STATB is turned on again
when charging restarts.
Figure 4 — SC811 Thermal Limiting Example
Notice the BAT output current is rapidly reduced to limit
the internal die temperature, then continues to decline as
the circuit board gradually heats up, further reducing the
conduction of heat from the die to the ambient environ-
ment. The fast thermal limiting feature ensures compliance
with CCSA YD/T 1591-2006, Telecommunication Industrial
Standard of the People’s Republic of China — Technical
Requirements and Test Method of Charger and Interface for
Mobile Telecommunication Terminal , Section 4.2.3.1.
Alternatively, the SC813 is offered for users who want to
limit OVP to a guaranteed maximum of 6V. The SC811 and
SC813 are alike except for OVP threshold.
Short Circuit Protection
The SC811/3 can tolerate a BAT pin short circuit to ground
indefinitely. The current into a ground short is approxi-
mately 10mA.
? 2008 Semtech Corporation
19
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相关代理商/技术参数 |
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| 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 |
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