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参数资料
| 型号： | LTC6992CDCB6-2#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO6 |
| 封装： | 2 X 3 MM, LEAD FREE, PLASTIC, MO-229TBD, DFN-6 |
| 文件页数： | 11/32页 |
| 文件大小： | 322K |
| 代理商： | LTC6992CDCB6-2#PBF |
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LTC6992-1/LTC6992-2/
LTC6992-3/LTC6992-4
19
69921234p
Basic Operation
The simplest and most accurate method to program the
LTC6992 is to use a single resistor, RSET, between the
SET and GND pins. The design procedure is a four step
process. After choosing the POL bit setting and proper
LTC6992 version, select the NDIV value and then calculate
the value for the RSET resistor.
Step 1: Selecting the POL Bit Setting
Most applications will use POL = 0, resulting in a positive
transfer function. However, some applications may require a
negative transfer function, where increasing VMOD reduces
the output duty cycle. For example, if the LTC6992 is used
in a feedback loop, POL = 1 may be required to achieve
negative feedback.
Step 2: Selecting the LTC6992 Version
The difference between the LTC6992 versions is observed
at the endpoints of the duty cycle control range. Applica-
tions that require the output never stop oscillating should
use the LTC6992-2. If it is better to allow the output to
rest at GND or V+ (0% or 100% duty cycle, respectively),
select the LTC6992-1.
The LTC6992-3 and LTC6992-4 clamp the duty cycle at
only one end of the control range, allowing the output to
stop oscillating at the other extreme. If POL = 1 the clamp
will swap from low duty cycle to high, or vice-versa. Refer
to Table 2 and Figure 4 for assistance in selecting the
proper version.
Step 3: Selecting the NDIV Frequency Divider Value
As explained earlier, the voltage on the DIV pin sets the
DIVCODE which determines both the POL bit and the
NDIV value. For a given output frequency, NDIV should be
selected to be within the following range.
62.5kHz
fOUT
≤ NDIV ≤
1MHz
fOUT
(1a)
To minimize supply current, choose the lowest NDIV value
(generally recommended). For faster start-up or decreased
jitter, choose a higher NDIVsetting.Alternatively,useTable1
as a guide to select the best NDIV value for the given ap-
plication.
APPLICATIONS INFORMATION
With POL already chosen, this completes the selection of
DIVCODE. Use Table 1 to select the proper resistor divider
or VDIV/V+ ratio to apply to the DIV pin.
Step 4: Calculate and Select RSET
The final step is to calculate the correct value for RSET
using the following equation.
RSET =
1MHz 50k
NDIV fOUT
(1b)
Select the standard resistor value closest to the calculated
value.
Example: Design a PWM circuit that satisfies the following
requirements:
fOUT = 20kHz
Positive VMOD to duty cycle response
Output can reach 100% duty cycle, but not 0%
Minimum power consumption
Step 1: Selecting the POL Bit Setting
For positive transfer function (duty cycle increases with
VMOD), choose POL = 0.
Step 2: Selecting the LTC6992 Version
To limit the minimum duty cycle, but allow the maximum
duty cycle to reach 100%, choose LTC6992-4. (Note that
if POL = 1 the LTC6992-3 would be the correct choice.)
Step 3: Selecting the NDIV Frequency Divider Value
Choose an NDIV value that meets the requirements of
Equation (1a).
3.125 ≤ NDIV ≤ 50
Potential settings for NDIV include 4 and 16. NDIV = 4 is
the best choice, as it minimizes supply current by us-
ing a large RSET resistor. POL = 0 and NDIV = 4 requires
DIVCODE = 1. Using Table 1, choose the R1 and R2 values
to program DIVCODE = 1.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC6992CDCB6-2-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox Voltage-Controlled Pulse Width Modulator (PWM) |
| LTC6992CDCB6-3-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox Voltage-Controlled Pulse Width Modulator (PWM) |
| LTC6992CDCB6-3-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox Voltage-Controlled Pulse Width Modulator (PWM) |
| LTC6992CDCB6-4-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox Voltage-Controlled Pulse Width Modulator (PWM) |
| LTC6992CDCB6-4-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:TimerBlox Voltage-Controlled Pulse Width Modulator (PWM) |
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