High speed, Low dropout, ±1% High output accuracy Dual CMOS Voltage Regulator
Rev. E13-01
VRD Series
DESCRIPTION OF OPERATION
ò General operation
In reference to following a part of the block diagram of output voltage control of the VRD series ;
*1)
V
IN
V
OUT
Over-current
Protector
R1
RDIS
VFEEDBACK
R2
+
VREF
Voltage
Reference
_
Error Amp.
V
SS
EN
By the error amplifier, the reference voltage (VREF) is compared with VFEEDBACK which is divided by
feedback resistors R1 and R2. It supplies the output transistor (see note *1) to keep a stabilized output
voltage against with any fluctuation of input voltage by negative feedback system.
Note *1)
The VRD series has P-channel MOSFET which is connected to the VOUT terminal as the output
transistor. To prevent the VRD series from being damaged due to inverse current from VOUT
terminal to VIN terminal through a parasitic diode, VOUT should not be exceeded VIN+0.3V.
ò EN terminal (shutdown function) & CL auto-discharge
The VRD series can be shutdown through EN terminal. The P-channel MOSFET is turned off and
operation of all internal circuits stops to reduce the current consumption when the signal of EN
terminal is set to the shutdown level. In shutdown mode, the VRD series enables the electric charge at
the C
L to be discharged via the auto-discharge resistance (RDIS ; 160Ω), and the VOUT terminal can be
rapidly returned to the VSS level as a result.
ò Output capacitor (C
For phase compensation, an output capacitor (C
SS terminal as close as possible. A ceramic capacitor with capacitance value of at least 1.0µF is
L)
L) is required to connected between VOUT terminal and
V
recommended. Of course, the suitable capacitance value should be different by the condition of each
application. In addition, an input capacitor (CIN) with capacitance value of at least 1.0µF is also
recommended between VIN terminal and VSS terminal for stable input power.
ò Over current protection and short circuit protection
Built-in over current protection circuit performs circuit protection from over current as a current limiter.
When the load current reaches the limit level, the output voltage drops and output current also
decreases accordingly. A current of typ. 40mA will flow when output terminal is shorted.
AnaSem
9
.......... Future of the analog world
www.anasemi.com
sales@anasemi.com
ANASEM [ AnaSem Hong Kong Limited ]
