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參數資料
| 型號： | RT9702 |
| 英文描述： | Power Management/Switchers |
| 中文描述： | 電源管理/切換器 |
| 文件頁數： | 13/16頁 |
| 文件大?。?/td> | 240K |
| 代理商： | RT9702 |
Preliminary
RT9702/A
DS9702A-01 March 2003
www.richtek.com
13
The faster trip time of the RT9702/A power distribution
allow designers to design hubs that can operate
through faults. The RT9702/A have low on-resistance
and internal fault-reporting circuitry that help the
designer to meet voltage regulation and fault
notification requirements. Because the devices are also
power switches, the designer of self-powered hubs has
the flexibility to turn off power to output ports. Unlike a
normal MOSFET, the devices have controlled rise and
fall times to provide the needed inrush current limiting
required for the bus-powered hub power switch.
Supply Filter/Bypass Capacitor
A 1μF low-ESR ceramic capacitor from V
IN
to GND,
located at the device is strongly recommended to
prevent the input voltage drooping during hot-plug
events. However, higher capacitor values will further
reduce the voltage droop on the input. Furthermore,
without the bypass capacitor, an output short may
cause sufficient ringing on the input (from source lead
inductance) to destroy the internal control circuitry. The
input transient
must
not exceed 6.5V of the absolute
maximum supply voltage even for a short duration.
Output Filter Capacitor
A low-ESR 150
μ
F aluminum electrolytic or tantalum
between V
OUT
and GND is strongly recommended to
meet the 330mV maximum droop requirement in the
hub V
BUS
(Per USB 2.0, output ports must have a
minimum 120
μ
F of low-ESR bulk capacitance per hub).
Standard bypass methods should be used to minimize
inductance and resistance between the bypass
capacitor and the downstream connector to reduce EMI
and decouple voltage droop caused when downstream
cables are hot-insertion transients. Ferrite beads in
series with V
BUS
, the ground line and the 0.1
μ
F bypass
capacitors
at
the
power
recommended for EMI and ESD protection. The bypass
capacitor itself should have a low dissipation factor to
allow decoupling at higher frequencies.
connector
pins
are
Fault Flag Filtering (Optional)
The
transient
capacitance may cause a short-duration error flag,
which may cause erroneous over-current reporting. A
simple 1mS RC low-pass filter (10K
and 0.1
μ
F) in the
flag line (see Typical Application Circuit) eliminates
short-duration transients.
inrush
current
to
downstream
Voltage Drop
The USB specification states a minimum port-output
voltage in two locations on the bus, 4.75V out of a
Self-Powered Hub port and 4.40V out of a
Bus-Powered Hub port. As with the Self-Powered Hub,
all resistive voltage drops for the Bus-Powered Hub
must be accounted for to guarantee voltage regulation
(see Figure 7-47 of Universal Serial Specification
Revision 2.0 ).
The following calculation determines
V
OUT (MIN)
for multi-
ple ports (
N
PORTS
) ganged together through one switch
(if using one switch per port,
N
PORTS
is equal to 1):
V
OUT (MIN)
= 4.75V – [ I
I
x ( 4
R
CONN
+ 2
R
CABLE
) ] –
( 0.1A x N
PORTS
x R
SWITCH
) – V
PCB
Where
R
CONN
= Resistance of connector contacts
(two contacts per connector)
R
CABLE
= Resistance of upstream cable wires
(one 5V and one GND)
R
SWITCH
= Resistance of power switch
(80m
typical for RT9702/A)
V
PCB
= PCB voltage drop
The USB specification defines the maximum resistance
per contact (
R
CONN
) of the USB connector to be 30m
and the drop across the PCB and switch to be 100mV.
This basically leaves two variables in the equation: the
resistance of the switch and the resistance of the cable.
If the hub consumes the maximum current (
I
I
) of 500mA,
the maximum resistance of the cable is 90m
.
The resistance of the switch is defined as follows:
R
SWITCH
= { 4.75V – 4.4V – [ 0.5A x ( 4
30m
+ 2
90m
) ] –V
PCB
}
÷
( 0.1A x N
PORTS
)
= (200mV – V
PCB
)
÷
( 0.1A x N
PORTS
)
相關PDF資料 |
PDF描述 |
|---|---|
| RT9702A | Power Management/Switchers |
| RT9801A | Power Management/Voltage Dector |
| RT9801B | Power Management/Voltage Dector |
| RT9802A | Power Management/Voltage Dector |
| RT9802B | Power Management/Voltage Dector |
相關代理商/技術參數 |
參數描述 |
|---|---|
| RT9702_11 | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:80m??, 500mA/1.1A High Side Power Switches with Flag |
| RT9702A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Power Management/Switchers |
| RT9702AGB | 功能描述:IC PWR SW USB 1.5A SOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 電源分配開關 系列:- 特色產品:XRP252 Switches 標準包裝:1 系列:- 類型:高端開關 輸出數:2 Rds（開）:140 毫歐 內部開關:是 電流限制:1.15A 輸入電壓:1.75 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-WFDFN 裸露焊盤 供應商設備封裝:10-TDFN（3x3） 包裝:Digi-Reel® 其它名稱:1016-1691-6 |
| RT9702AGJ5 | 功能描述:IC PWR SW USB 1.1A TSOT-23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 電源分配開關 系列:- 特色產品:XRP252 Switches 標準包裝:1 系列:- 類型:高端開關 輸出數:2 Rds（開）:140 毫歐 內部開關:是 電流限制:1.15A 輸入電壓:1.75 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-WFDFN 裸露焊盤 供應商設備封裝:10-TDFN（3x3） 包裝:Digi-Reel® 其它名稱:1016-1691-6 |
| RT9702APB | 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:80mヘ, 500mA/1.1A High-Side Power Switches with Flag |
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