BRCD3408
Rev.E Apr.-2018
描述
/
Descriptions
DATA SHEET
BRCD3408 是一款恒定频率、电流脉冲½度调制模式的降压½换器。该器件集成了一个主控开关和同
步整流器替换肖特基二极管，
½芯片具有更高效½。
它是½用单节锂电池供电的便携式设备的理想选择，
输出电压最½可调节至 0.6V。BRCD3408 在½压状态下以 100%占空比模式运行，延长便携式系统电
池寿½。该器件提供 PWM（脉冲½度调制）和 PFM（脉冲频率调制）两种可切换的操½模式，可以
在广泛负½½范围内高效运行。
The BRCD3408 is a constant frequency, current mode PWM step-down converter. The device
integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky
diode. It is ideal for powering portable equipment that runs from a single cell Lithium-Ion (Li+) battery.
The output voltage can be regulated as low as 0.6V. The BRCD3408 can also run at 100% duty cycle
for low dropout operation, extending battery life in portable system. This device offers two operation
modes, PWM control and PFM Mode switching control, which allows a high efficiency over the wider
range of the load
特征
/ Features
高效率高达 96%，1.5MHz 恒频工½，输出电流 1.2A，输入工½电压范围：2.5V~6.0V, 输出电压½至
0.6V, 短路保护，过温保护，浪涌电流限制和½启动，关断电流：＜1µA。
High Efficiency: Up to 96% ,1.5MHz Constant Frequency Operation,1.2A Output Current, 2.5V to 6.0V
Input Voltage Range, Output Voltage as Low as 0.6V, Short Circuit Protection, Thermal Fault
Protection, Inrush Current Limit and Soft Start, <1µA Shutdown Current.
用途
/
Applications
手机和智½电话，无线及 DSL 调制解调器，个人数字助手（掌上电脑）/移动互联½设备/平板电脑，
数码相机与摄像机。
Cellular and Smart Phones, Wireless and DSL Modems, PDA/MID/PAD, Digital Still and Video
Cameras.
典型应用电路图
/ Typical Application
Figure 1. Basic Application Circuit
Load Current(A)
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BRCD3408
Rev.E Apr.-2018
DATA SHEET
引脚排列
/ Pinning
5
1
2
3
4
引脚
PIN
1
2
名称
NAME
EN/RUN
功½
FUNCTION
½½端，驱动电压高于1.5V时打开，½于0.3V是关断，不½悬空。
Chip Enable Pin. Drive RUN above 1.5V to turn on the part. Drive RUN
below 0.3V to turn it off. Do not leave RUN floating
接地端
Ground Pin
电源开关输出端。该引脚与器件内部P型和N型MOSFET的漏极连接，外部
需要与电感连接。
Power Switch Output. It is the switch node connection to Inductor. This pin
connects to the drains of the internal P-ch and N-ch MOSFET switches
电源输入端。靠近引脚处必须连接去耦电容，该电容可以是4.7µF或更大的
陶瓷电容。
Power Supply Input. Must be closely decoupled to GND with a 4.7µF or
greater ceramic capacitor
输出电压反馈输入端。通过一个内部电阻分压器将输出电压与内部参考电
压进行比较。
Output Voltage Feedback Pin. An internal resistive divider divides the
output voltage down for comparison to the internal reference voltage
GND
3
LX/SW
4
VIN
5
FB
印章代码
/ Marking
见印章说明。
See Marking Instructions.
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BRCD3408
Rev.E Apr.-2018
极限参数
DATA SHEET
/ Absolute Maximum Ratings(Ta=25℃)
符号
Symbol
V
IN
V
EN
V
LX
I
P
P
D
T
J
T
L
T
opr
T
stg
数值
Rating
-0.3 to +6.3
-0.3
-0.3
1.8
600
155
300
-40 to +85
-65 to +150
单½
Unit
V
V
V
A
mW
℃
℃
℃
℃
参数
Parameter
Supply Input voltage(Note1)
EN/VOUT Voltages
LX Voltage
Peak LX Sink and Source Current
Power Dissipation
Junction Temperature(Note2)
Lead Temperature (Soldering,10s)
Operating Temperature
Storage Temperature
电性½参数
/ Electrical Characteristics( V
IN
=V
RUN
=3.6V, V
OUT
=1.8V, T
A
= 25°C, unless otherwise
noted.)(Note3)
参数
Parameter
Input Voltage Range
OVP Threshold
UVLO Threshold
Input DC Supply Current
PWM Mode
PFM Mode
Shutdown Mode
Regulated Feedback Voltage
Reference Voltage Line Regulation
Output Voltage Line Regulation
Output Voltage Load Regulation
Oscillation Frequency
On Resistance of PMOS
ON Resistance of NMOS
Peak Current Limit
RUN Threshold
Vout=100%
Vout=0V
ILX=100mA
ILX=-100mA
VIN= 3V, Vout=90%
0.30
测试条件
Test Conditions
最小值 典型值
Min
Typ
2.5
6.5
2.0
Vout = 90%, Iload=0mA
Vout = 105%, Iload=0mA
VRUN=0V, VIN=4.2V
(Note4)
TA = 25°C
TA = 0°C
≤
TA
≤
85°C
TA = -40°C
≤
TA
≤
85°C
Vin=2.5V to 6.0V
Vin=2.5V to 6.0V
0.588
0.586
0.585
140
40
0.1
0.600
0.600
0.600
0.04
0.04
0.5
1.5
300
0.25
0.10
1.8
1.0
1.50
0.30
0.15
300
65
1.0
0.612
0.613
0.615
0.40
0.4
最大值
Max
6.0
单½
Unit
V
V
V
µA
µA
µA
V
V
V
%/V
%
%
MHz
KHz
Ω
Ω
A
V
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BRCD3408
Rev.E Apr.-2018
DATA SHEET
电性½参数
/ Electrical Characteristics( V
IN
=V
RUN
=3.6V, V
OUT
=1.8V, T
A
= 25°C, unless otherwise
noted.)(Note3)
参数
Parameter
RUN Leakage Current
LX Leakage Current
OS_EN
OS_SW
OS_VIN
OS_FB
UVLO
undervoltage
protection
voltage
Iq1 pulse width modulation mode
current
Iq2 pulse frequency modulation
mode current
Isd quiescent current
Vfb feedback voltage accuracy
SV1
电压调整率
SV2
电压调整率
Notes:
1：超出最大绝对额定值，可½损坏器件
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
2：结温 T
J
是通过环境温度值 T
A
和功耗值 P
D
根据以下公式计算得出
T
J
=T
A
+（P
D
）×（250°C/W）
T
J
is calculated from the ambient temperature T
A
and power dissipation P
D
according to the
following formula:
T
J
= T
A
+（P
D
）×（250°C
/ W）
3：25°C 的参数值是经过 100%测试得出。规格书上的温度范围可以通过相关的设计和控制方法来保证
100% production test at +25°C. Specifications over the temperature range are guaranteed by
design and characterization
4：在栅极电荷被输送在开关频率时动态电源电流较高
Dynamic supply current is higher due to the gate charge being delivered at the switching
frequency
测试条件
Test Conditions
VRUN=0V,VIN=VLX=5V
I=-100uA
I=-100uA
I=-100uA
I=-100uA
V
IN
=2.7V,V
RUN
=2.5V
V
IN
=V
RUN
=3.6V,FB=0.3V
V
IN
=V
RUN
=3.6V,FB=1V
V
IN
==3.6V,VRUN=0V
V
IN
=V
RUN
=3.6V
V
IN
=2.5V-6V,V
RUN
=2.5V
V
IN
=2.5V-6V,V
RUN
=2.5V
0.588
-0.9
-0.9
-0.9
-0.9
2
300
50
1
0.612
0.40%
0.40%
最小值 典型值
Min
Typ
±0.01
±0.01
最大值
Max
±1.0
±1.0
-0.3
-0.3
-0.3
-0.3
单½
Unit
µA
µA
V
V
V
V
V
uA
uA
uA
V
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BRCD3408
Rev.E Apr.-2018
功½框图
/
Functional Block Diagram
DATA SHEET
图2.BRCD3408功½框图
Figure 2. BRCD3408 Block Diagram
功½描述 /
Functional Description
BRCD3408是一种高性½的1.2A、1.5MHz单片式的降压½换器。该BRCD3408只需要三个外部功率
元件（CIN，COUT和L）
。可调版本可根据外部的反馈进行编程，输出从0.6V到输入电压之间的任½
电压。
The BRCD3408 is a high performance 1.2A 1.5MHz monolithic step-down converter. The
BRCD3408 requires only three external power components (Cin, Cout and L). The adjustable
version can be programmed with external feedback to any voltage, ranging from 0.6V to the input
voltage.
在½输入电压情况下，½换器的占空比上升到100％，输出电压等于输入电压减去导通压降较高的一
个MOSFET的电压。内部误差放大器和补偿器具有出色的瞬态响应特性，及时对负½½电压进行线性调
整。½启动功½有效防止启动过程中的输入浪涌电流和输出过冲。
At dropout, the converter duty cycle increases to 100% and the output voltage tracks the input
voltage minus the R
dson
drop of the high-side MOSFET. The internal error amplifier and
compensation provides excellent transient response, load, and line regulation. Soft start function
prevents input inrush current and output overshoot during start up。
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