rev.
page
date
2 of 11
08/2007
PART NUMBER:
VPOL5A-5-SMT
DESCRIPTION:
point of load converter
Q1
+VIN
L1
+VO
1. Introduction
This application note describes the features and functions of V-Infinity’s
VPOL5A-5-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-5-SMT series provide precisely regulated output voltage range
from 0.75V to 3.63 Vdc over a wide range of input voltage (Vi=3.0 – 5.5
Vdc) and can operate over an ambient temperature range of –40
+85
synchronous rectification and drive control techniques.
The modules are fully protected against short circuit and over-
temperature conditions. V-Infinity’s world class automated
manufacturing methods, together with an extensive testing and
qualification program, ensure that all VPOL5A-5-SMT series converters
are extremely reliable.
to
. Ultra-high efficiency operation is achieved through the use of
ON/OFF
COM
COM
C1
Q2
D1
C2
R1
PWM IC
ERR AMP
R trim
TRIM
R2
Figure 1. Electrical Block Diagram
3.2 Thermal Packaging and Physical Design.
The VPOL5A-5-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.
2. VPOL5A-5-SMTConverter Features
High efficiency topology, typically 94% at 3.3 Vdc
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
3.63 Vdc
No minimum load requirement (Stable at all loads)
Remote ON/OFF
Remote sense compensation
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-5-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-5-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-5-
SMT series converters do not draw any reverse current at start-up. The
output voltage can be adjusted from 0.75 to 3.63vdc, 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.
20050
SW
112
th
Ave. Tualatin, Oregon
97062
phone
503.612.2300
fax
503.612.2382
CUI [ CUI INC ]
