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RZ3111A Schematic ( PDF Datasheet ) - Wuxi Microelectronics

Teilenummer RZ3111A
Beschreibung PWM Control 3A Step-Down Converter
Hersteller Wuxi Microelectronics
Logo Wuxi Microelectronics Logo 




Gesamt 7 Seiten
RZ3111A Datasheet, Funktion
RZ3111A
PWM Control 3A Step-Down Converter
GENERAL DESCRIPTION
RZ3111A consists of step-down switching regulator with PWM control. These devise include a
reference voltage source, oscillation circuit, error amplifier, internal PMOS and etc.
RZ3111A provides low-ripple power, high efficiency, and excellent transient characteristics. The
PWM control circuit is able to the duty ratio linearly form 0 up to 100%. This converter is build out soft
start function that prevents overshoot and inrush current at startup. An over current protect function and
short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency
will be reduced. The operating frequency is decided by outside resistance. An external compensation is
easily to system stable.
With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected
externally, these ICs can function as step-down switching regulators. They serve as ideal power supply
units for portable devices when coupled with the SOP8-EP with exposed pad package, providing such
outstanding features as low current consumption. Since this converter can accommodate an input
voltage up to 40V, it is also suitable for the operation via an AC adapter.
FEATURES
- Input voltage 4.2V to 40V
- Output voltage 0.8V to 38V
- Duty ratio 0% to 100% PWM control
- Oscillation frequency range is 50K 500KHz by outside resistance setting
- Current Limit, Short Circuit Protect (SCP) and Thermal Shutdown protection
- Built-in internal SW P-channel MOS.
- SOP8-EP Pb-Free package.
Block Diagram
FB
OCSET
COMP
OSC
Reference Voltage
Source with Soft Start
Vcc
+
Oscillation
Circuit
PWM-Switched
Control Circuit
Thermal
VEN Shutdown
EN
SW
60uA VSS
V1.0 2010-10
Tel. 0510-85898501 18061979821 Fax. 0510-85898500
1/7






RZ3111A Datasheet, Funktion
RZ3111A
PWM Control 3A Step-Down Converter
Output Capacitor Selection
The output capacitor is required to filter the output and provide regulator loop stability. The important
capacitor parameters are; the 100 KHz Equivalent Series Resistance (ESR), the RMS ripples current
rating, voltage rating, and capacitance value. For the output capacitor, the ESR value is the most
important parameter. The ESR can be calculated from the following formula.
V RIPPLE = IL ×ESR= 0.6A x 80m= 48mV
An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating.
In most case, higher voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors
with much higher voltage ratings may be needed to provide the low ESR values required for low output
ripple voltage. It is recommended to replace this low ESR capacitor by using a 470µF low ESR values <
80m.
Demoboard PCB layout
V1.0 2010-10
Tel. 0510-85898501 18061979821 Fax. 0510-85898500
6/7

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