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参数资料
| 型号： | ISL6111CRZA |
| 厂商： | INTERSIL CORP |
| 元件分类： | 电源管理 |
| 英文描述： | Current Regulated PCI Hot Plug Power Switch Controller |
| 中文描述： | 3-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| 封装： | 5 X 5 MM, LEAD-FREE, PLASTIC, MO-220VHHC, QFN-20 |
| 文件页数： | 9/16页 |
| 文件大小： | 480K |
| 代理商： | ISL6111CRZA |
9
The average current on the -12V supply should not
exceed 0.8A. Since the thermal restrictions on the +12V
supply are more severe, the +12V supply restricts the use
of the ISL6111 to applications where the
±
12V supplies
draw relatively little current. Since both supplies only have
one degree of freedom, the value of R
OCSET
, the
flexibility of programming is quite limited. For applications
where more power is required on the +12V supply,
contact your local Intersil sales representative for
information on other Hot Plug solutions.
B.
Do not
try to sense voltages across the external sense
resistors that are less than 20mV as spurious faults due
to noise and comparator input sensitivity may result. The
minimum recommended R
CRSET
value is 3.0k
. This
will set the nominal OC voltage thresholds at 39mV and
26mV for the 3.3V and 5V comparators respectively.
C. Minimize V
RSENSE
so as to not significantly reduce the
voltage delivered to the adapter card. Remember PCB
trace and connector distribution voltage losses also need
to be considered. Make sure that the R
SENSE
resistor
can adequately handle the dissipated power. For best
results use a 1% precision resistor with a low temperature
coefficient.
D. Minimize external FET r
DS(ON)
. Low r
DS(ON)
or multiple
MOSFETs in parallel are recommended.
Current Regulation Delay Time to Latch-Off
The CR time delay to latch-off, allows for a predetermined
delay from the start of CR, to the simultaneous latch-off of all
four supply switches to the load. This delay period is set by
the capacitor value to ground from the CRTIM pin. This
feature allows the ISL6111 to provide a current regulated soft
start into all loads, and to delay immediate latch-off of the
bus supply switches thus ignoring transient OC conditions.
See Table 2. for CR duration vs CRTIM capacitance value.
Caution:
An additional concern about long CR durations
along with MB supply droop is power-FET survivability. The
primary purpose of a protection device such as the ISL6111
is to quickly isolate a faulted card from the voltage bus.
Delaying the time to latch-off works against this primary
concern so understand the limitations and realities. Since we
use the same CRTIM cap timing cap for all supplies, we
have to set that cap to a size large enough to allow the -12V
to start up under the worst load for a given system. If we set
this to a 75ms duration, then this 75ms time-out duration will
also be used when one of the higher power supplies goes
into current limiting after startup is complete. The highest
power supplies, the 3.3V and 5V each run to a maximum of
25W, as allowed by the PCI spec. If our overcurrent duration
is set to 75ms, then theoretically (but extremely unlikely)
more than 25W can be dissipated in the external FET for that
whole duration. The ISL6111 has a way over-current "WOC"
circuit that faults the chip off instantly if this theoretical dead
short happens so quickly that the current limiting circuitry
can't keep up. In reality, overcurrent is more likely to not be a
zero-ohm short, and only a fraction of the power is
dissipated in the FET.
Ensure adequate sizing of external FETs to carry additional
current during CR period in linear operation. By looking at
the SOA of the Siliconix Si4404DY FET and even
presupposing the full 25W for 100ms duration for a single
pulse is not an issue with this power FET. This FET is
representative of FETs for a PCI application. If for a higher
power non PCI design, consult the MOSFET vendor SOA
curves.
Application Considerations
Soft Start and Turn-Off Considerations
The ISL6111 does allow the user to select the rate of ramp
up on the voltage supplies. This start-up ramp minimizes in-
rush current at start-up while the on card bulk capacitors
charge. The ramp is created by placing capacitors on
M12VG, 3VG and 5VG to ground. These capacitors are each
charged up by a nominal 25
μ
A current during turn on. The
+12VO has internal current controlled ramping circuitry. The
same value for all gate timing capacitors is recommended.
The gate capacitors must be discharged when a fault is
detected to turn off the power FETs thus, larger caps slow
the response time. If the gate capacitors are too large the
ISL6111 may not be able to adequately protect the bus or the
power FETs. The ISL6111 has internal discharge FETs to
discharge the load when disabled. Upon turn-off these
internal switches on each output discharge the load
capacitance pulling the output to gnd. These switches are
also on when ENABLE is low thus an open slot is held at the
gnd level.
Recommended PCB Layout Design
To ensure accurate current sensing and control, the PCB
traces that connect each of the current sense resistors to the
ISL6111 must not carry any load current. This can be
accomplished by two dedicated PCB kelvin traces directly
from the sense resistors to the ISL6111, see examples of
correct and incorrect layouts below in Figure 2. To reduce
TABLE 1.
SUPPLY
NOMINAL CURRENT REGULATION LEVEL (10%)
FOR EACH SUPPLY
+3.3V I
CR
((100
μ
A x R
CRSET
)/8.54)/R
RSENSE
+5.0V I
CR
((100
μ
A x R
CRSET
)/12)/R
RSENSE
+12V I
CR
(100
μ
A x R
CRSET
)/0.7
-12V I
CR
(100
μ
A x R
CRSET
)/3.3
TABLE 2.
CRTIM, VALUE
0.022F
0.1
μ
F
1
μ
F
Nominal CR Duration
3.3ms
15ms
150ms
Nominal CR Duration = 150k
X TIM cap value.
ISL6111
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| ISL6111CRZA-T | 功能描述:热插拔功率分布 W/ANNEAL 20LD MLFP 5X5 PCI HOTSWAP CNTR RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| ISL6111EVAL2 | 功能描述:EVALUATION BOARD 2 FOR ISL6111 RoHS:否 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 标准包装:1 系列:PCI Express® (PCIe) 主要目的:接口，收发器，PCI Express 嵌入式:- 已用 IC / 零件:DS80PCI800 主要属性:- 次要属性:- 已供物品:板 |
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