LR2257 Datasheet, PDF (1/8 Pages) Leshan Radio Company – AC/DC Current Mode PWM power management controller

LESHAN RADIO COMPANY, LTD.
LR2257 _{AC/DC Current Mode PWM}
power management controller
The LR2257 AC—DC is a high
efficiency current-mode PWM power
supply controller that drives an internal
NPN transistor for high voltage switching.
Apply with BiCMOS technology, the
device consist of Bandgap reference
voltage, Oscillator, High voltage switching
transistor and build in safety features of
over current and over voltage protection
mechanisms
Delivering up to 3W yet consumes, the
typical application of the device will
include:
z Battery Charger, such as handset phone
z Power Adapter
z Offline Power Generator
z Etc.
¾ Lowest Total Cost Solution
¾ Low Power for Green Environments
Protection, as lower as 0.3W
¾ Current Mode PWM
¾ Over-Current Protection, Over and
Under-voltage Protection
¾ Emitter Drive of Internal Power Transistor
¾ 65kHz Switching Frequency
Absolute Maxim Ratings
Item
Power Supply
FB Start Voltage
FB Under-voltage Threshold
FB Clamp Voltage
FB input current
Switching Frequency
Maximum Duty Cycle
FB－SW Current Gain
Current Limit
SW Break Down Voltage
Stand By Current
System Efficiency (Full Load)
Symbol
VDD
Vs
Vu
Vo
I_FB
Fs
D_MAX
G_F
I_LIM
Vsw
P_S
η
Typical
9～12
5
3.5
5.5
<1
65
75
0.3
400
>400
<0.3W
>70
Unit
V
V
V
V
mA
KHz
％
A/V
mA
V
W
%
1/8