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| 型号： | ZL2008ALBFT1 |
| 厂商： | Intersil |
| 文件页数： | 21/42页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 36-QFN |
| 标准包装： | 1,000 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1.4MHz |
| 占空比： | 95% |
| 电源电压： | 3 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 36-VFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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ZL2008
D ( V IN ? max ? V OUT ) + ( 1 ? D ) ? V OUT
=
R 1 ? min
C L (which is the average I OUT DCR product) is small and can be
neglected. Therefore, the minimum value of R 1 may be
approximated Equation 26: ,
2 2
(EQ. 26)
P R 1 pkg ? max ? δ P
ZL
GH
SW
ISENA
V IN
V OUT
GL
where P R1pkg- max is the maximum power dissipation
specification for the resistor package and P is the derating factor
for the same parameter (eg.: P R1pkg- max = 0.0625W for 0603
package, P = 50% @ 85°C). Once R 1- min has been calculated,
ISENB
MOSFET R DS(ON) Sensing
V IN
C L ? max =
L
(EQ. 27)
R 1 ? min ? DCR
and choose the next-lowest readily available value (e.g.: For
C L- max = 1.86μF, C L = 1.5μF is a good choice). Then substitute
the chosen value into the same equation and re-calculate the
value of R 1 . Choose the 1% resistor standard value closest to this
re-calculated value of R 1 . The error due to the mismatch of the
two time constants is expressed in Equation 28:
GH
SW
ZL
GL
ISENA
ISENB
Inductor DCR Sensing
(V OUT must be less than 4.0 V)
V OUT
R 1 ? C L ? DCR ? ?
ε τ = ? ? 1 ?
? 100 %
?
R 2 = 5 ? R 1
?
(EQ. 28)
? L avg ?
The value of R 2 should be simply five times that of R 1 :
(EQ. 29)
For the R DS(ON) current sensing method, the external low side
MOSFET will act as the sensing element as indicated in
Figure 16.
Current Limit Threshold Selection
It is recommended that the user include a current limiting
mechanism in their design to protect the power supply from
damage and prevent excessive current from being drawn from
the input supply in the event that the output is shorted to ground
or an overload condition is imposed on the output. Current
limiting is accomplished by sensing the current through the
circuit during a portion of the duty cycle.
Output current sensing can be accomplished by measuring the
voltage across a series resistive sensing element according to
Equation 30:
FIGURE 16. Current Sensing Methods
To set the current limit threshold, the user must first select a
current sensing method. The ZL2008 incorporates two methods
for current sensing, synchronous MOSFET R DS(ON) sensing and
inductor DC resistance (DCR) sensing; Figure 16 shows a
simplified schematic for each method. The current sensing
method can be selected using the CFG2 pin, as shown in
Tables 26 and 28, or via the I 2 C/SMBus interface. Please refer to
Application Note AN2033 for details.
In addition to selecting the current sensing method, the ZL2008
gives the power supply designer several choices for the fault
response during over or under current condition. The user can
select the number of violations allowed before declaring fault, a
blanking time and the action taken when a fault is detected.
The blanking time represents the time when no current
measurement is taken. This is to avoid taking a reading just after
a switching transition (less accurate due to potential ringing). It is
a configurable parameter.
Once the sensing method has been selected, the user must
select the voltage threshold (VLIM), the desired current limit
V LIM = I LIM × R SENSE
Where:
(EQ. 30)
threshold, and the resistance of the sensing element.
The current limit threshold voltage can be selected by simply
connecting the ILIM pin as shown in Table 14. The ground-
I LIM is the desired maximum current that should flow in the
circuit.
R SENSE is the resistance of the sensing element.
V LIM is the voltage across the sensing element at the point the
circuit should start limiting the output current.
referenced sensing method is being used in this mode. By
default, the IOUT_CAL_GAIN is set to 1m Ω for DCR mode and
2m Ω for RDS mode.
TABLE 14. Current Limit Threshold Voltage Pin-strap Settings
R DS V LIM DCR V LIM
ILIM Pin (mV) (mV)
The ZL2008 supports “lossless” current sensing by measuring
the voltage across a resistive element that is already present in
the circuit. This eliminates additional efficiency losses incurred
by devices that must use an additional series resistance in the
circuit.
21
LOW
OPEN
HIGH
50
60
70
25
30
35
FN6859.4
April 29, 2011
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ZL2008EVAL1Z | 功能描述:EVALUATION BOARD FOR ZL2008 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 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 |
| ZL20200 | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:Dual Band IS136/AMPS Transceiver |
| ZL20200_06 | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:Dual Band IS136/AMPS Transceiver |
| ZL20200LCE | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:Dual Band IS136/AMPS Transceiver |
| ZL20200LCF | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:Dual Band IS136/AMPS Transceiver |
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