20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2382
1. Introduction
This application note describes the features and functions of #5)).#gS
VPOL5A-12-SMT series of non-isolated dc-dc converters. These are
highly efficient, reliable and compact, high power density, single output
DC/DC converters. These “Point of Load” modules serve the needs
specifically of the fixed and mobile telecommunications and computing
market, employing economical distributed Power Architectures. The
VPOL5A-12-SMT series provide precisely regulated output voltage
range from 0.75V to 5.0Vdc over a wide range of input voltage (Vi=8.3 –
14Vdc) and can operate over an ambient temperature range of –40°C
to +85°C. Ultra-high efficiency operation is achieved through the use of
synchronous rectification and drive control techniques.
The modules are fully protected against short circuit and over-
temperature conditions. #5)).#gS world class automated
manufacturing methods, together with an extensive testing and
qualification program, ensure that all VPOL5A-12-SMT series
converters are extremely reliable.
2.VPOL5A-12-SMT Converter Features
High efficiency topology, typically 89% at 3.3Vdc
Industry standard footprint
Wide ambient temperature range, -40°C to +85°C
Cost efficient open frame design
Programmable output voltage via external resistor from 0.75 to
5.0Vdc
No minimum load requirement (Stable at all loads)
Remote ON/OFF
Fixed switching frequency
Continuous short-circuit protection and over current protection
Over-temperature protection (OTP)
Monotonic Startup with pre-bias at the output.
UL/IEC/EN60950 Certified.
3. General Description
3.1 Electrical Description
A block diagram of the VPOL5A-12-SMT series converter is shown in
Figure 1. Extremely high efficiency power conversion is achieved
through the use of synchronous rectification and drive techniques.
Essentially, the powerful VPOL5A-12-SMT series topology is based on
a non-isolated synchronous buck converter. The control loop is
optimized for unconditional stability, fast transient response and a very
tight line and load regulation. In a typical pre-bias application the
VPOL5A-12-SMT series converters do not draw any reverse current at
start-up. The output voltage can be adjusted from 0.75 to 5.0vdc, using
the TRIM pin with a external resistor. The converter can be shut down
via a remote ON/OFF input that is referenced to ground. This input is
compatible with popular logic devices; a 'positive' logic input is supplied
as standard. Positive logic implies that the converter is enabled if the
remote ON/OFF input is high (or floating), and disabled if it is low. The
converter is also protected against over-temperature conditions.
If the converter is overloaded or the ambient temperature gets too
high, the converter will shut down to protect the unit.
C1 C2
Q2
Q1
D1
L1
+VIN
COM COM
+VO
PWM IC
R1
R2
R trim
ERR AMP
ON/OFF TRIM
Figure 1. Electrical Block Diagram
3.2 Thermal Packaging and Physical Design.
The VPOL5A-12-SMT series uses a multi-layer FR4 PCB construction.
All surface mount power components are placed on one side of the
PCB, and all low-power control components are placed on the other
side. Thus, the heat dissipation of the power components is optimized,
ensuring that control components are not thermally stressed. The
converter is an open-frame product and has no case or case pin. The
open-frame design has several advantages over encapsulated closed
devices. Among these advantages are:
Efficient Thermal Management: the heat is removed from the
heat generating components without heating more sensitive, small
signal control components.
Environmental: Lead free open-frame converters are more easily
re-cycled.
Cost Efficient: No encapsulation. Cost efficient open-frame
construction.
Reliable: Efficient cooling provided by open frame construction
offers high reliability and easy diagnostics.
rev.
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date
rev.
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DESCRIPTION: point of load converter
2 of 12
08/2007
PART NUMBER: VPOL5A-12-SMT
For more information, please visit the product page.