NXP Semiconductors
AN11641
Relay replacement by NXP high-power bipolar transistors in LFPAK56
1. Introduction
NXP's bipolar power transistors in LFPAK use the latest BISS (Breakthrough In Small
Signal) transistor technology. They include mesh-emitter-design technology IP-platform to
achieve high-power devices with low V
CEsat
(saturation collector-emitter voltage) voltage
drop and high current gain. By this upmarket development, NXP wants to extend its
powerful and successful BISS transistor portfolio into the medium power and power range
in order to reach full traction for its high-power low V
CEsat
and high-current mesh-emitter
technology. To achieve this aim NXP uses a package supporting the high power
dissipation demand of its transistor portfolio. LFPAK offers superior low thermal
impedance Z
th
and therefore high thermal power capability up to 5 W.
Key parameters are current distribution (which should be as homogenous as possible)
over chip volume, and little spreading resistance in the metallization on the front of the
chip. In the case of BISS transistors, a homogeneous current distribution in the chip is
achieved by the latest mesh-emitter-design technology IP-platform, which breaks the
transistor down into corresponding cell structures. Soft-solder capable front and back
metallization combine this wafer technology with the LFPAK-package platform
requirements introducing new-developed metal stack interfaces for chip front and back
interface. They are optimized for low-resistivity contact of all transistor terminals to the
package outline.
The high-performance/high-reliability package platform LFPAK provides clip-bond for
emitter and base contact. This achieves low electrical and thermal resistivity of the
devices on all terminals. The electrical package resistivity is below 1 m. The overall
thermal impedance of the power transistors in the current chip-size range is below 6 K/W.
Soft-solder die and clip attach establish a rugged package architecture with up to
T
j(max)
= 175
C
high-temperature capability.
1.1 Features and benefits
•
High power dissipation (P
tot
)
•
Suitable for high-temperature applications (175 °C)
•
Space-saving 5
6
mm: package outline is half the size of equivalent transistors in
DPAK, SOT223, and other packages
•
•
•
•
•
Low profile (1 mm)
High reliability and mechanical ruggedness thanks to solid copper clip (no wires)
High energy efficiency due to less heat generation
AEC-Q101 qualified
Future-proof, growing portfolio
AN11641
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2015. All rights reserved.
Application note
Rev. 1 — 21 May 2015
3 of 16
NXP Semiconductors
AN11641
Relay replacement by NXP high-power bipolar transistors in LFPAK56
2. Brushed DC motor control
Modern DC motors are used in various applications:
•
•
•
•
•
•
Power windows
Wipers
Blower motors (heating / cooling)
Trunk lifter
Steering wheel adjustment
Seat adjustment
A lot of these applications are using relays for driving the brushed DC motor. This
application note shows which parameter must be taken into account to replace relays by
bipolar transistors in H-bridge configuration controlled by a Pulse Width
Modulation (PWM) signal.
The used DC brushed motor for this application note has following characteristics:
•
Nominal operating voltage: 12 V
•
Nominal operating current: 3 A
•
Blocked operating current: 8 A
2.1 Relay operation
GND
K2
GND
M
K1
12 V
K2
K1
12 V
aaa-017884
Every tactile switch turns a relay on and the motor turns left or right.
Fig 1.
Relay schematic
AN11641
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2015. All rights reserved.
Application note
Rev. 1 — 21 May 2015
4 of 16
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