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參數(shù)資料
| 型號： | LM3370TL-2613/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.4 A DUAL SWITCHING CONTROLLER, 2400 kHz SWITCHING FREQ-MAX, PBGA20 |
| 封裝： | 3 X 2 MM, 0.60 MM HEIGHT, 0.50 MM PITCH, , MO-211DG, MICRO, SMD-20 |
| 文件頁數(shù)： | 14/26頁 |
| 文件大?。?/td> | 5436K |
| 代理商： | LM3370TL-2613/NOPB |
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Application Information
SETTING OUTPUT VOLTAGE VIA I2C-compatible
The outputs of the LM3370 can be programmed through Buck
1 & Buck 2 registers via I2C. Buck 1 output voltage can be
dynamically adjusted between 1V to 2V in 50 mV steps and
Buck 2 output voltage can be adjusted between 1.8V to 3.3V
in 100 mV steps. Finer adjustments to the output of Buck 2
can be achieved with the placement of a resistor betweeen
VOUT2 and the FB2 pin. Typically by placing a 20 K
resistor,
R, between these nodes will result in the programmed Output
Voltage increasing by approximately 45 mV,
ΔV
TYP.
ΔV
TYP= R × 500mV / 234K
Please refer to for programming the desire output voltage. If
the I2C-compatible feature is not used, the default output volt-
age will be the pre-trimmed voltage. For example,
LM3370SD-3021 refers to 1.2V for Buck 1 and 3.3V for Buck
2.
V
DD Pin
V
DD is the power supply to the internal control circuit, if VDD
pin is not tied to V
IN during normal operating condition, VDD
must be set equal or greater of the two inputs ( V
IN1 or VIN2 ).
An optional capacitor can be used for better noise immunity
at V
DD pin or when VDD is not tied to either VIN pins. Addition-
ally, for reasons of noise suppression, it is advisable to tie the
EN1/EN2 pins to V
DD rather than VIN .
SDA, SCL Pins
When not using I2C the SDA and SCL pins should be tied
directly to the V
DD pin.
Micro-Stepping:
The Micro-Stepping feature minimizes output voltage over-
shoot/undershoot during large output transients. If Micro-
stepping is enabled through I2C, the output voltage automat-
ically ramps at 50 mV per step for Buck 1 and 100 mV per
step for Buck 2. The steps are summarized as follow:
Buck 1: 50 mV/step and 32 s/step
Buck 2: 100 mV/step and 32 s/step
For example if changing Buck 1 voltage from 1V to 1.8V yields
20 steps [(1.8 - 1)/ 0.05 = 20]. This translates to 640
μs [(20
x 32 s) = 640 s] needed to reach the final target voltage.
INDUCTOR SELECTION
There are two main considerations when choosing an induc-
tor; the inductor should not saturate, and the inductor current
ripple is small enough to achieve the desired output voltage
ripple.
There are two methods to choose the inductor current rating.
method 1:
The total current is the sum of the load and the inductor ripple
current. This can be written as
I
LOAD load current
V
IN input voltage
L inductor
f switching frequency
method 2:
A more conservative approach is to choose an inductor that
can handle the maximum current limit of 1400 mA.
Given a peak-to-peak current ripple (I
PP) the inductor needs
to be at least
A 2.2 H inductor with a saturation current rating of at least
1400 mA is recommended for most applications. The
inductor’s resistance should be less than around 0.2
for
good efficiency. Table 2 lists suggested inductors and sup-
pliers.
For low-cost applications, an unshielded bobbin inductor is
suggested. For noise critical applications, a toroidal or shield-
ed-bobbin inductor should be used. A good practice is to lay
out the board with overlapping footprints of both types for de-
sign flexibility. This allows substitution of a low-noise toroidal
inductor, in the event that noise from low-cost bobbin models
is unacceptable.
Below are some suggested inductor manufacturers include
but are not limited to:
TABLE 2. Suggested Inductors and Suppliers
Model
Vendor
Dimensions
(mm)
I
SAT
DO3314-222
Coilcraft
3.3 x 3.3 x 1.4
1.6A
LPO3310-222
3.3 x 3.3 x 1.0
1.1A
SD3114-2R2
Cooper
3.1 x 3.1 x 1.4
1.48A
NR3010T2R2M Taiyo Yuden
3.0 x 3.0 x 1.0
1.1A
NR3015T2R2M
3.0 x 3.0 x 1.5
1.48A
VLF3010AT-
2R2M1R0
TDK
2.6 x 2.8 x 1.0
1.0A
INPUT CAPACITOR SELECTION
A ceramic input capacitor of 4.7
μF, 6.3V is sufficient for most
applications. A larger value may be used for improved input
voltage filtering. The input filter capacitor supplies current to
the PFET switch of the LM3370 in the first half of each cycle
and reduces voltage ripple imposed on the input power
source. A ceramic capacitor's low ESR provides the best
noise filtering of the input voltage spikes due to this rapidly
changing current. Select an input filter capacitor with a surge
current rating sufficient for the power-up surge from the input
power source. The power-up surge current is approximately
the capacitor’s value (F) times the voltage rise rate (V/s).
The input current ripple can be calculated as:
OUTPUT CAPACITOR SELECTION
DC bias characteristics of ceramic capacitors must be con-
sidered when selecting case sizes like 0805 and 0603. DC
21
www.national.com
LM3370
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3370TL-3006 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual Synchronous Step-Down DC-DC Converter with Dynamic Voltage Scaling Function |
| LM3370TL-3006/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM3370TL-3008 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual Synchronous Step-Down DC-DC Converter with Dynamic Voltage Scaling Function |
| LM3370TL-3008/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM3370TL-3008EV | 功能描述:低壓差穩(wěn)壓器 - LDO LM3370 Eval Brd RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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