参数资料
| 型号： | ISL6227IRZ |
| 厂商： | Intersil |
| 文件页数： | 21/27页 |
| 文件大小： | 0K |
| 描述： | IC CONTROLLER DDR, DDR2 28QFN |
| 标准包装： | 60 |
| 应用： | 控制器，DDR，DDR2 |
| 输入电压： | 5 V ~ 28 V |
| 输出数： | 2 |
| 输出电压： | 0.9 V ~ 5.5 V |
| 工作温度： | -40°C ~ 100°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-VFQFN 裸露焊盘 |
| 供应商设备封装： | 28-QFN 裸露焊盘（5x5） |
| 包装： | 管件 |
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ISL6227
Application Information
Design Procedures
GENERAL
A ceramic decoupling capacitor should be used between the
VCC and GND pin of the chip. There are three major
currents drawn from the decoupling capacitor:
1. the quiescent current, supporting the internal logic and
normal operation of the IC
2. the gate driver current for the lower MOSFETs
3. and the current going through the external diodes to the
bootstrap capacitor for upper MOSFET.
In order to reduce the noisy effect of the bootstrap capacitor
current to the IC, a small resistor, such as 10 Ω , can be used
with the decoupling capacitor to construct a low pass filter for
the IC, as shown in Figure 41. The soft-start capacitor and
the resistor divider setting the output voltage is easy to
TO BOOT
current of the ISEN pin to meet the overcurrent protection
and the change the current loop gain. The lower the current
sensing resistor, the higher gain of the current loop, which
can damp the output LC filter more.
A higher value current-sensing resistor will decrease the
current sense gain. If the phase node of the converter is very
noisy due to poor layout, the sensed current will be
contaminated, resulting in duty cycle jittering by the current
loop. In such a case, a bigger current sense resistor can be
used to reduce both real and noise current levels. This can
help damp the phase node wave form jittering.
Sometimes, if the phase node is very noisy, a resistor can be
put on the ISEN pin to ground. This resistor together with the
R CS can divide the phase node voltage down, seen by the
internal current sense amplifier, and reduce noise coupling.
Sizing the Overcurrent Setpoint Resistor
The internal 0.9V reference is buffered to the OCSET pin
with a voltage follower (refer to the equivalent circuit in
Figure 42). The current going through the external
overcurrent set resistor is sensed from the OCSET pin. This
5V
10 Ω
VCC
current, divided by 2.9, sets up the overcurrent threshold and
compares with the scaled ISEN pin current going through
R CS with an 8μA offset. Once the sensed current is higher
than the threshold value, an OC signal is generated. The first
OC signal starts a counter and activates a pulse skipping
FIGURE 41. INPUT FILTERING FOR THE CHIP
Selection of the Current Sense Resistor
The value of the current sense resistor determines the gain
of the current sensing circuit. It affects the current loop gain
and the overcurrent protection setpoint. The voltage drop on
the lower MOSFET is sensed within 400ns after the upper
MOSFET is turned off. The current sense pin has a 140 Ω
resistor in series with the external current sensing resistor.
The current sense pin can source up to a 260μA current
while sensing current on the lower MOSFET, in such a way
function. The inductor current will be continuously monitored
through the phase node voltage after the first OC trip. As
long as the sensed current exceeds the OC threshold value,
the following PWM pulse will be skipped. This operation will
be the same for 8 switching cycles. Another OC occurring
between 8 to 16 switching cycles would result in a latch off
with both upper and lower drives low. If there is no OC within
8 to 16 switching cycles, normal operation resumes.
that the voltage drop on the current sensing path would be
equal to the voltage on the MOSFET.
PHASE
ISEN 140 Ω
-
+ 8uA
I SOURCING ( R CS + 140 Ω ) = I D r DS ( ON )
(EQ.17)
_
+
R CS
r DS(ON)
+
+
Σ
8μA
+33.1
I D can be assumed to be the inductor peak current. In a
worst case scenario, the high temperature r DS(ON) could
increase to 150% of the room temperature level. During
overload condition, the MOSFET drain current I D could be
R SET
OC SET
-
+
0.9V
AMPLIFIER REFERENCE
+2.9
I SENSE
+ OC
-
COMPARATOR
130% higher than the normal inductor peak. If the inductor
has 30% peak-to-peak ripple, I D would equal to 115% of the
load current. The design should consider the above factors
so that the maximum I SOURCING will not saturate to 260μA
under worst case conditions. To be safe, I SOURCING should
be less than 100μA in normal operation at room
temperature. The formula in the earlier discussion assumes
a 75μA sourcing current. Users can tune the sourcing
21
FIGURE 42. EQUIVALENT CIRCUIT FOR OC SIGNAL
GENERATOR
FN9094.7
May 4, 2009
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL6227IRZ-T | 功能描述:IC CONTROLLER DDR, DDR2 28QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
| ISL6228 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:High-Performance Dual-Output Buck Controller for Notebook Applications |
| ISL6228EVAL3Z | 功能描述:EVALUATION BOARD FOR ISL6228 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:Robust Ripple Regulator™ (R³) 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL6228HIEVAL3Z | 功能描述:EVALUATION BOARD FOR ISL6228HI RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:Robust Ripple Regulator™ (R³) 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL6228HRTZ | 功能描述:IC REG CTRLR BUCK PWM 28-TQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:Robust Ripple Regulator™ (R³) 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
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