DC527A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
LT3433
DESCRIPTION
Demonstration circuit 527 is a monolithic step-up / stepdown DC/DC switching converter with Burst Mode™ featuring the LT3433. The board is optimized for 5V output
at up to 400mA load current (12VIN) and an input voltage range of 4V to 60V. With its wide input voltage
range, 500mA internal power switches, 100µA quiescent
current during Burst Mode, 200kHz switching frequency
and thermally enhanced package, the LT3433 is a very
versatile and powerful IC for DC/DC converters that require both step-up and step-down capability for 5VOUT
as well as compact space, high efficiency, low cost, and
tolerance to high input voltage transients.
The LT3433 200kHz switching frequency allows all of the
components to be small, surface mount devices. The
current-mode control topology creates fast transient
response and good loop stability with a minimum number of external components. The SHDN pin can be used
to program undervoltage lockout or place the part in micropower shutdown, reducing supply current to 10µA
(25µA maximum) by driving the pin low. Burst Mode
operation is jumper selectable for extremely low, light
load quiescent current.
The LT3433 datasheet gives a complete description of
the part, operation and applications information. The
datasheet must be read in conjunction with this Quick
Start Guide for demonstration circuit 527. The LT3433 is
assembled in a small 16-pin thermally enhanced package with exposed pad. Proper board layout is essential
for maximum thermal performance.
Design files for this circuit board are available. Call
the LTC factory.
Burst Mode is a trademark of Linear Technology Corporation.
Table 1. Typical Performance Summary (TA = 25°C)
PARAMETER
CONDITION
Input Voltage Range
Zero Load Input Current
VOUT
Maximum Output Current
Output Voltage Ripple
Light Load Output Voltage Ripple
Switching Frequency
Efficiency
VALUE
4–60V
Burst Mode ON, IOUT = 0A, VIN = 12V
120µA
Burst Mode OFF, IOUT = 0A, VIN = 12V
1.0mA
VIN = 4V to 60V, ISW(PK) ≤ 500mA
5V ± 3%
VIN = 4V, VOUT = 5V
125mA
VIN = 12V, VOUT = 5V
400mA
VIN = 48V, VOUT = 5V
340mA
VIN = 4V, VOUT = 5V, IOUT = 125mA
75mVPK–PK
VIN = 12V, VOUT = 5V, IOUT = 400mA
25mVPK–PK
VIN = 48V, VOUT = 5V, IOUT = 340mA
35mVPK–PK
VIN = 12V, VOUT = 5V, IOUT = 5mA, Burst Mode ON
18mVPK–PK
VIN = 12V, VOUT = 5V, IOUT = 5mA, Burst Mode OFF
7mVPK–PK
VIN = 4V to 60V, VOUT = 5V
200kHz
VIN = 4V, IOUT = 100mA, VOUT = 5V
58%
VIN = 12V, IOUT = 400mA, VOUT = 5V
80%
VIN = 48V, IOUT = 300mA, VOUT = 5V
71%
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
QUICK START PROCEDURE
Demonstration circuit 527 is easy to set up to evaluate
the performance of the LT3433. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
NOTE: Make sure that the input voltage does not exceed
60V.
NOTE: The shutdown function is optional and its pin can
be left floating (disconnected) if not being used.
NOTE: Do not hot-plug the input voltage terminal VIN. The
absolute maximum voltage on VIN is 60V and hotplugging a power supply through wire leads to the demonstration card can cause the voltage on the extremely
low-ESR ceramic input capacitor to ring to twice its DC
value. This is due to high currents instantaneously generated in the inductive supply leads from an input voltage step on the low-ESR ceramic input capacitor. A
bulky higher-ESR capacitor, and an additional inductive
filter can be added to the circuit to dampen hot-plug
transient ringing. See Application Note 88 for more details. A transient voltage suppressor diode may also be
used to absorb transient overvoltage.
1. Connect the power supply (with power off), load, and
meters as shown in Figure 1.
2. After all connections are made, turn on input power
and verify that the output voltage is 5V.
NOTE: If the output voltage is too low, temporarily disconnect the load to make sure that the load is not set
too high.
3. Once the proper output voltages are established, ad-
just the loads within the operating range and observe
the output voltage regulation, ripple voltage, efficiency
and other parameters.
Figure 1. Proper Measurement Equipment Setup
CUSTOM OPTIONS
OUTPUT VOLTAGE
The components assembled on the board are optimized
for a wide input voltage range and a 5V output. The
feedback resistors (R2, R3) can be changed to adjust the
output voltage according to the following equation:
VOUT = 1.23 (1 + R2/R3)
COMPENSATION
Demonstration Circuit 527 has a frequency compensation network that is optimized for the tantalum output
capacitor C5, the wide input voltage range 4V to 60V,
and 5V output. Improved loop bandwidth can be
achieved for various output voltages, output capacitors,
and input voltage ranges by adjusting R1, C4, and C3.
For more information, see the ‘Frequency Compensation’
section in the Application Note 19 or Application Note
76.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
SOFT START
The soft start capacitor C6 controls the peak switch current during startup by holding down the output of the
error amplifier as it charges up. The soft start capacitor
forces the peak switch current to start at zero. Output
voltage overshoot can be reduced or eliminated using
this capacitor. The time that it takes for the converter to
reach maximum available current is
TSS = 2.7*105 * CSS
BURST MODE OPERATION
Jumper selectable Burst Mode operation provides the
tradeoff of low quiescent current at light loads or low
ripple voltage at light loads. Figure 2 demonstrates the
increased efficiency using Burst Mode at light loads. As
the load gets lighter and lighter the effect is increased.
At zero load, the quiescent current of the IC is reduced
to only 100µA with Burst Mode enabled. The effect of
Burst Mode ripple current at light loads is shown in
Figure 7. Extremely low, light load ripple voltage can be
achieved by disabling Burst Mode.
12VIN
100%
90%
80%
EFFICIENCY
70%
Burst_En ON
60%
50%
40%
4VIN
30%
20%
Burst_En OFF
10%
0%
0.1
1
10
100
1k
LOAD CURRENT (mA)
Figure 2. DC527 Typical Efficiency (TA = 25°C)
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
500
MAXIMUM LOAD CURRENT (mA)
450
BUCK
400
350
300
CONTINUOUS INDUCTOR CURRENT
250
BUCK/BOOST
200
150
100
DISCONTINUOUS INDUCTOR CURRENT
50
0
0
5 10 15 20 25 30 35 40 45 50 55 60
VIN (V)
Figure 3. DC527 Maximum Load Current is Typically 400mA to 300mA in Buck Mode and 125mA to 200mA
in Bridged Mode (Buck and Boost).
Figure 4. DC527 Output Voltage Ripple in Bridged Mode
(IOUT = 125mA, VIN = 4V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
Figure 5. DC527 Output Voltage Ripple in Buck Mode (IOUT = 400mA, VIN = 12V, VOUT = 5V, TA = 25°C) CH1
is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L
Figure 6. DC527 Output Voltage Ripple Buck Mode
(IOUT = 300mA, VIN = 48V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
Figure 7. DC527 Output Voltage Ripple Burst Mode at Light Load with Burst Mode
(IOUT = 5mA, VIN = 12V, VOUT = 5V, TA = 25°C) CH1 is VOUT ripple, CH2 is VSW_H, CH3 is VSW_L
Figure 8. DC527 Step Load Response (IOUT = 100mA to 300mA, VIN = 12V, TA = 25°C, VOUT = 5V) CH2 is
VOUT ripple, CH4 is IOUT
6
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
Figure 9. DC527 VOUT Soft Start-Up with 10nF CSS (RLOAD = 12.5Ω, VIN = 12V, TA = 25°C) CH2 is VOUT, CH1
is VSW_H
7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 527
STEP-UP / STEP-DOWN CONVERTER WITH BURST MODE
8
5
4
3
2
1
REVISION HISTORY
LTC CONFIDENTIAL - For Customer Use Only
ECO
REV
DESCRIPTION
DATE
PROTO
6
APPROVED
06/09/03
VOUT
D
2
D
D1
D3
B160
1N4148WS
L1
100uH
0.1uF
D2
3
CDRH6D28-101
4
+ C9
4V to 60V
VOUT
13
VBIAS
12
[1]
D4
1
1
3
C7
6
VC
TP2
C6
10nF
Css
C3
R1
68k
330pF
5
VFB
7
SGND4
SS
SGND3
10
BURST_EN
PWRGND
GND
+ C5
R2
14
R3
100k
1%
LOAD CURRENT TABLE
C4
1nF
B
UNLESS OTHERWISE SPECIFIED
DIMENSIONS ARE IN INCHES
TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL
PER ASME Y14.5M -1994
NOTES: UNLESS OTHERWISE SPECIFIED,
[1]
DO NOT INSTALL; C9, C10
A
THIRD ANGLE PROJECTION
CONTRACT NO.
APPROVALS
DRAWN MEI
C
47uF
10V
305k
16
SHDN
SGND2
11
[email protected]
SEE LOAD
CURRENT
TABLE
TP6
2
1N4148WS
0.1uF
2 JP1
TP4
VOUT
C10
B120
BURST_EN
ON
OFF
LT3433EFE
9
SHDN
SW_L
15
U1
SGND1
GND
C2
2.2uF
100V
R5
100k
[1]
VIN
8
C
VIN
BOOST
1
VIN
TP3
SW_H
2
TP1
VOUT
1
C1
DATE
05-30-02
CHECKED
TECHNOLOGY
TITLE
APPROVED
VIN
IOUT (MAX)
4V
125mA
12V
400mA
24V
360mA
48V
340mA
B
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
SCH, LT3433EFE STEP-UP/ STEP-DOWN
CONVERTER WITH BURST MODE
A
ENGINEER
DESIGNER
SIZE CAGE CODE
DO NOT SCALE DRAWING
5
4
Monday, June 23, 2003
3
SCALE: NONE
DWG NO
REV
6
DC527A
A
FILENAME: 527A-6.DSN
2
SHEET
1
1
OF
1
Linear Technology Corporation LT3433EFE
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Qty
1
1
1
1
1
1
1
0
1
1
2
1
1
1
1
1
1
0
5
1
1
Ref
C1
C2
C3
C4
C5
C6
C7
C9,C10
D1
D2
D4,D3
JP1
L1
R1
R2
R3
R5
R6
TP1,TP2,TP3,TP4,TP6
U1
JP1
Parts List
Desc
CAP, X7R 0.1uF 16V 10% 0603
CAP, X7R 2.2uF 100V 10% 1812
CAP, NPO 330pF 50V 5% 0402
CAP, X7R 1000pFuF 50V 10% 0603
CAP, TANT 47uF 10V 20% 6032
CAP, X7R 0.01uF 100V 10% 0603
CAP, X7R 0.1uF 16V 10% 0805
DO NOT STUFF
DIODE, B160
DIODE, B120
DIODE, SWITCHING
HEADER, 3PIN, 2mm
IND, 100uH
RES, 68k OHMS 5% 1/16W 0603
RES, 305k OHMS 1% 1/16W 0402
RES, 100k OHMS 1% 1/16W 0402
RES, 100k OHMS 1% 1/16W 0603
DO NOT STUFF
TURRET
IC, LT3433EFE
SHUNT, 2PIN, 2mm
1 of 1
DC527A Rev 6
6/24/2003
Manufacturer / Part #
AVX 0603YC104KAT
TDK C4332X7R2A225K
AVX 04025C331JAT
AVX 06035C102KAT
AVX TPSC476M010R0350
AVX 06031C103KAT
AVX 0805YC104KAT1A
OPTION
DIODES INC. B160
DIODES INC. B120
DIODES INC. 1N4148WS
COMM CON 2802S-03G2
SUMIDA CDRH6D28-101
AAC CR16-683JM
AAC CR05-3053FM
AAC CR05-1003FM
AAC CR16-1003FM
NONE
MILL-MAX-2501-2
LINEAR TECH LT3433EFE
COMM CON CCIJ2MM-138G
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