AN2565
Application note
PM6680A evaluation kit
dual step-down controller with auxiliary voltages
Introduction
PM6680A evaluation kit order code: STEVAL-ISA053V2.
The PM6680A is a dual step-down controller with adjustable output voltages. The PM6680A
evaluation kit is designed to test the performance of the PM6680A by employing a typical
application circuit that allows testing of all the PM6680A device functions. The kit features
two switching sections, with (typically) 3.3 V and 1.8 V outputs, from a 6 V to 36 V input
voltage. The typical operating switching frequency of the two switching sections is 200 kHz /
300 kHz, respectively. Each switching section delivers more than 2.5 A of output current.
Moreover, an internal linear regulator can provide 5 V @ 100 mA peak current.
Figure 1.
PM6680A evaluation kit
April 2008
Rev 2
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Contents
AN2565
Contents
1
2
3
4
5
6
7
8
9
10
Main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Evaluation kit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Evaluation board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
I/O interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Recommended equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Quick start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Jumper settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Feedback output connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Test setup and performance summary . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Power-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Soft-start and shutdown waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
OUT1 and OUT2 output efficiency vs. load current . . . . . . . . . . . . . . . . . 19
Power consumption analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Switching frequency vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Linear regulator output voltages vs. output current . . . . . . . . . . . . . . . . . 24
Load transient response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
11
12
Representative waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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AN2565
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
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Figure 24.
Figure 25.
Figure 26.
Figure 27.
PM6680A evaluation kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Evaluation kit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PM6680A eval board layout - top layer (PGND plane and component side) . . . . . . . . . . . . 8
PM6680A eval board layout - inner layer 1 (SGND layer and V
IN
plane) . . . . . . . . . . . . . . . 8
PM6680A eval board layout - inner layer 2 (SGND layer and signals) . . . . . . . . . . . . . . . . . 9
PM6680A eval board layout - bottom layer (PM6680A and component side) . . . . . . . . . . . 9
Test setup connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Power-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Section 1 soft-start waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Section 2 soft-start waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Section 1 shutdown waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Section 2 shutdown waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
OUT1 efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
OUT2 efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Device current consumption vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Device current consumption vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
OUT1 switching frequency vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
OUT2 switching frequency vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
LDO5 output vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
OUT1 load transient response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
OUT2 load transient response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SMPS pulse skip mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
SMPS no-audible skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
SMPS PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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Main features
AN2565
1
Main features
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Constant on-time control allows very fast load transients
6 V to 36 V input voltage range
5 V auxiliary output voltage
Adjustable switching outputs
Lossless current sensing using low side MOSFET R
DS(on)
Negative current limit
Soft-start internally fixed at 2.8 ms
Soft-end for output discharge
200 kHz / 300 kHz, 300 kHz / 400 kHz, 400 kHz / 500 kHz (OUT1 / OUT2 selectable
switching frequency)
Selectable pulse skip and no-audible skip modes at light loads
Independent power good signals
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AN2565
Evaluation kit schematic
2
Evaluation kit schematic
Figure 2.
Evaluation kit schematic
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