- 您现在的位置：买卖IC网 > PDF目录44990 > LTC3108IGN-1#PBF (LINEAR TECHNOLOGY CORP) SWITCHING REGULATOR, PDSO12 PDF资料下载
参数资料
| 型号： | LTC3108IGN-1#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PDSO12 |
| 封装： | 0.150 INCH, LEAD FREE, PLASTIC, SSOP-16 |
| 文件页数： | 9/24页 |
| 文件大小： | 1593K |
| 代理商： | LTC3108IGN-1#PBF |
LTC3108-1
31081f
applicaTions inForMaTion
Design Example 1
This design example will explain how to calculate the
necessary storage capacitor value for VOUT in pulsed
load applications, such as a wireless sensor/transmit-
ter. In these types of applications, the load is very small
for a majority of the time (while the circuitry is in a low
power sleep state), with bursts of load current occur-
ring periodically during a transmit burst. The storage
capacitor on VOUT supports the load during the transmit
burst, and the long sleep time between bursts allows
the LTC3108-1 to recharge the capacitor. A method for
calculating the maximum rate at which the load pulses
can occur for a given output current from the LTC3108-1
will also be shown.
In this example, VOUT is set to 3V, and the maximum al-
lowed voltage droop during a transmit burst is 10%, or
0.3V. The duration of a transmit burst is 1ms, with a total
average current requirement of 40mA during the burst.
Given these factors, the minimum required capacitance
on VOUT is:
C
F
mA ms
V
F
OUT(
)
.
≥
=
40
1
0 3
133
Note that this equation neglects the effect of capacitor
ESR on output voltage droop. For most ceramic or low
ESR tantalum capacitors, the ESR will have a negligible
effect at these load currents.
A standard value of 150F or larger could be used for COUT
in this case. Note that the load current is the total current
draw on VOUT, VOUT2 and VLDO, since the current for all of
theseoutputsmustcomefromVOUTduringaburst.Current
contribution from the holdup capacitor on VSTORE is not
considered, since it may not be able to recharge between
bursts. Also, it is assumed that the charge current from
the LTC3108-1 is negligible compared to the magnitude
of the load current during the burst.
To calculate the maximum rate at which load bursts can
occur, determine how much charge current is available
from the LTC3108-1 VOUT pin given the input voltage
source being used. This number is best found empirically,
since there are many factors affecting the efficiency of
the converter. Also determine what the total load cur-
rent is on VOUT during the sleep state (between bursts).
Note that this must include any losses, such as storage
capacitor leakage.
Assume, for instance, that the charge current from the
LTC3108-1 is 50A and the total current drawn on VOUT
in the sleep state is 17A, including capacitor leakage. In
addition, use the value of 150F for the VOUT capacitor.
The maximum transmit rate (neglecting the duration of
the transmit burst, which is typically very short) is then
given by:
t
F
V
A
or f
H
MAX
=
=
150
0 3
50
17
1 36
0 73
.
(
)
. sec
.
zz
Therefore, in this application example, the circuit can sup-
port a 1ms transmit burst every 1.3 seconds.
It can be determined that for systems that only need to
transmit every few seconds (or minutes or hours), the
average charge current required is extremely small, as
long as the sleep current is low. Even if the available
charge current in the example above was only 10A and
the sleep current was only 5A, it could still transmit a
burst every 9 seconds.
The following formula enables the user to calculate the
time it will take to charge the LDO output capacitor and
the VOUT capacitor the first time, from 0V. Here again, the
charge current available from the LTC3108-1 must be
known. For this calculation, it is assumed that the LDO
output capacitor is 2.2F.
t
V
F
I
LDO
CHG
LDO
=
2 2
.
.
If there were 50A of charge current available and a 5A
load on the LDO (when the processor is sleeping), the time
for the LDO to reach regulation would be 107ms.
If VOUT were programmed to 3V and the VOUT capacitor
was 150F, the time for VOUT to reach regulation would be:
t
V
F
I
t
VOUT
CHG
VOUT
LDO
=
+
3
150
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3108EGN-1#TRPBF | SWITCHING REGULATOR, PDSO12 |
| LTC3108EDE-1#PBF | SWITCHING REGULATOR, PDSO12 |
| LTC3112IDHD#PBF | 12 A SWITCHING REGULATOR, 825 kHz SWITCHING FREQ-MAX, PDSO16 |
| LTC3112IFE#PBF | 12 A SWITCHING REGULATOR, 825 kHz SWITCHING FREQ-MAX, PDSO20 |
| LTC3112EFE#PBF | 12 A SWITCHING REGULATOR, 825 kHz SWITCHING FREQ-MAX, PDSO20 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3108IGN-1-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Ultralow Voltage Step-Up Converter and Power Manager |
| LTC3108IGNPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Ultralow Voltage Step-Up Converter and Power Manager |
| LTC3108IGN-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Ultralow Voltage Step-Up Converter and Power Manager |
| LTC3108IGNTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Ultralow Voltage Step-Up Converter and Power Manager |
| LTC3108IGN-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Ultralow Voltage Step-Up Converter and Power Manager |
发布紧急采购，3分钟左右您将得到回复。