Instruction Manual for ANALOG DEVICES models including: LT8334, Low IQ Boost SEPIC Inverting Converter with 5A 40V Switch, LT8334 Low IQ Boost SEPIC Inverting Converter with 5A 40V Switch, EVAL-LT8334-AZ
DEMO MANUAL · EVAL-LT8334-AZ. Rev. 0. QUICK START PROCEDURE. Evaluation circuit EVAL-LT8334-AZ is easy to set up to evaluate the performance of the LT8334.
LT8334 Техническое описание и информация о продукте | Analog Devices
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DocumentDocumentDEMO MANUAL EVAL-LT8334-AZ
LT8334 Low IQ Boost/SEPIC/Inverting Converter with 5A, 40V Switch
DESCRIPTION
Evaluation circuit EVAL-LT8334-AZ features the LT®8334 in a SEPIC configuration. It operates with a switching frequency of 2MHz and is designed to convert a 3V to 26V source to 12V output. The converter can output up to 2.2A depending on the input voltage (see Figure 3 for the maximum output current vs VIN curve).
This evaluation circuit features Spread Spectrum Frequency Modulation (SSFM), EMI filters, and space for an option EMI shield to provide optimum EMI performance. This PCB layout is optimized for good EMI performance and small solution size. The evaluation board contains a selectable jumper, JP1, to aid in the selection of the desired SYNC pin mode of operation. At light load, either PULSE SKIP or low-ripple BURST mode can be selected to improve the efficiency.
The LT8334 boost/SEPIC/inverting converter IC operates over an input range of 2.8V to 40V, suitable for
automotive, telecom, and industrial applications. The converter provides adjustable and synchronizable operation from 300kHz to 2MHz with SSFM option. The LT8334 packs other popular features such as soft-start, bias pin, input undervoltage lockout. The IC can exhibit a low quiescent current down to 9A in BURST mode and 1A in shutdown, which makes it ideal for battery-operated systems. The LT8334 is assembled in a thermally enhanced 12-lead 4mm × 3mm DFN package.
The data sheet gives a complete description of the device, operation, and applications information. The data sheet must be read in conjunction with this demo manual for EVAL-LT8334-AZ.
Design files for this circuit board are available.
All registered trademarks and trademarks are the property of their respective owners.
BOARD PHOTO
Rev. 0
1
DEMO MANUAL EVAL-LT8334-AZ
PERFORMANCE SUMMARY Specifications are at TA = 25°C
PARAMETER
CONDITIONS
Input Voltage (VIN) Output Voltage (VOUT) Maximum Output Current (IOUT)
Switching Frequency (fSW)
VOUT = 12V R6 = 1M, R7 = 154k VOUT = 12V, VIN = 9V VOUT = 12V, VIN = 12V VOUT = 12V, VIN = 16V to 26V R2 = 20.0k, SSFM OFF R2 = 20.0k, SSFM ON
Input EN Voltage (Rising)
R3 = 1M, R1 = 1.15M
Input UVLO Voltage (Falling)
R3 = 1M, R1 = 1.15M
Typical Efficiency (with EMI Filters)
VIN = 9V, VOUT = 12V, IOUT = 1.75A
VIN = 12V, VOUT = 12V, IOUT = 2A
VIN = 16V, VOUT = 12V, IOUT = 2.2A
Zero Load Quiescent Current (VOUT = 12V)*
VIN = 12V, JP1 = BURST
R6 = 1M, R7 = 154k R3 = 1M, R1 = 1.15M
VIN = 12V, JP1 = PULSE SKIP VIN = 24V, JP1 = BURST
VIN = 24V, JP1 = PULSE SKIP
*Please see PULSE SKIP, BURST, SSFM, SYNC section on how to achieve lower quiescent current.
MIN
TYP
MAX
UNIT
3
26
V
12
V
1.75
A
2
A
2.2
A
2
MHz
2
2.4
MHz
3.2
V
3.0
V
86
%
87
%
87
%
35
µA
1.2
mA
33
µA
1.2
mA
Rev. 0
2
DEMO MANUAL EVAL-LT8334-AZ
QUICK START PROCEDURE
Evaluation circuit EVAL-LT8334-AZ is easy to set up to evaluate the performance of the LT8334. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below.
NOTE: Make sure that the input voltage is always with the specification.
1. Connect EN/UVLO turret to GND.
2. With power off, connect the input power supply to VIN and GND terminals of the board. Include voltage and current meters as shown in Figure 1 if desired.
3. Connect the load to the VOUT and GND terminals. 4. Turn on the power at the input. Increase VIN slowly
to 12V.
5. Disconnect EN/UVLO turret from GND and the output turns on.
6. Check for the proper output voltage. The output should be regulated at 12V.
If there is no output, temporarily disconnect the load to make sure that the load is not set too high.
7. Once the proper output voltage is established, adjust the input voltage and load current within the operating range and observe the output voltage regulation, ripple voltage, efficiency, and other parameters.
NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the input and output capacitors.
Figure 1. Proper Equipment Setup for EVAL-LT8334-AZ
Rev. 0
3
DEMO MANUAL EVAL-LT8334-AZ
QUICK START PROCEDURE
OUTPUT VOLTAGE AND POWER
The LT8334 is a low IQ non-synchronous DC/DC converter that can be configured in boost, SEPIC, or inverting converters. Although EVAL-LT8334-AZ is designed to regulate 12V output from a 3V-to-26V source, the feedback resistors R6 and R7 can be easily adjusted for higher or lower output voltage. In addition to adjusting feedback resistors, the input and output capacitors should be sized appropriately. The catch diode, D1, must also be able to handle the output voltage.
The 5A peak switch current limit allow a maximum 2.2A output current at 16VIN or higher. Figure 3 shows the maximum output current for versus VIN for DC operation.
PULSE SKIP, BURST, SSFM, SYNC
The LT8334 achieves low power consumption at light loads. The different SYNC/MODE pin states can be evaluated by changing the position of jumper JP1. It is easy to change from BURST to PULSE SKIP and to explore SSFM ON, SSFM OFF, and external SYNC with this jumper.
PULSE SKIP allows low quiescent current at light load consumption without changing switching frequency until a very light load. BURST allows the lowest light load power consumption and has a unique low ripple feature on the LT8334. These two features can be explored further in the data sheet of the LT8334. For even lower no-load input current, the EN/UVLO pin should be shorted to VIN and the R1 resistor should be removed. The feedback resistors, R6 and R7, can be replaced with higher resistance values for best no-load input current results.
Spread Spectrum Frequency Modulation (SSFM) can be enabled to reduce the emissions of the converter. SSFM spreads the frequency between the RT-programmed frequency and +20% higher.
If an external SYNC signal is provided, the SYNC option of JP1 can be used to synchronize with an external clock. The clock frequency should be slightly higher than the RT-programmed frequency for best performance.
EN/UVLO
R3 and R1 set the undervoltage lockout falling and rising thresholds. The LT8334 data sheet gives a formula for calculating these values. EVAL-LT8334-AZ has a falling UVLO threshold of 3V and a rising threshold of 3.2V. This threshold can easily be adjusted by changing resistors R3 and R1 according to the data sheet equations.
BIAS
In this evaluation circuit, the bias pin is unused and tied to GND through R5. However, the bias pin can be connected to an auxiliary input supply for powering INTVCC to improve efficiency when 4.4V BIAS VIN. To use the BIAS pin, R5 needs to be replaced by an 0402 sized ceramic capacitor with a value of at least 1µF, and BIAS terminal should be connected to the auxiliary source, which could be VOUT.
OUTPUT SHORT-CIRCUIT PROTECTION
The LT8334 configured in a SEPIC configuration protects the circuitry when the output is shorted. The EVALLT8334-AZ prevents damage to circuitry during quick transient output short circuits. However, the existing diode on the evaluation circuit is selected for optimal efficiency and quiescent current, but not for protecting continuous short-circuits. If continuous output short circuit protection is required, a diode with the current rating above the "Switch Overcurrent Threshold" stated in the data sheet is recommended.
Rev. 0
4
EFFICIENCY (%) MAXIMUM OUTPUT CURRENT (A)
TEST RESULTS
100
95
90
85
80
75
70
65
60
VIN = 5V
55
VIN = 12V
VIN = 16V
50
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2.0 2.2
LOAD CURRENT (A)
EVAL-8334 F02
Figure 2. EVAL-LT8334-AZ Efficiency at VOUT = 12V and Different VIN, EVAL-LT8334-AZ is Assembled with EMI Filters, JP1 = BURST
DEMO MANUAL EVAL-LT8334-AZ
2.5
2.0
1.5
1.0
0.5
0 2 4 6 8 10 12 14 16 18 20 22 24 26 INPUT VOLTAGE (V)
EVAL-8334 F03
Figure 3. EVAL-LT8334-AZ Steady State Maximum Output Current vs Input Voltage
(AC) VOUT 500mV/DIV
IOUT 1A/DIV
2A 1A
50s/DIV
EVAL-8334 F04
Figure 4. EVAL-LT8334-AZ VOUT Transient Response with VIN = 12V, VOUT = 12V, IOUT = 1A to 2A (JP1 = PULSE SKIP)
Figure 5. EVAL-LT8334-AZ Thermals at VIN = 12V, VOUT = 12V, IOUT = 2A
Rev. 0
5
DEMO MANUAL EVAL-LT8334-AZ
TEST RESULTS
AVERAGE CE (dBµV)
80
CLASS 5 AVERAGE LIMIT
70
EVAL-LT8334-AZ
60
EVAL-LT8334-AZ + SHIELD
AMBIENT
50
40
30
20
10
0
10
20 0.1
1
10
FREQUENCY (MHz)
108
EVAL-8334 F06
Figure 6. EVAL-LT8334-AZ CISPR25 Voltage Conducted EMI Average Performance with 12VIN to 12VOUT at 2A, JP1 = BURST+SSFM
AVERAGE RE (dBµV/m)
60
CLASS 5 AVERAGE LIMIT
50
EVAL-LT8334-AZ
EVAL-LT8334-AZ + SHIELD
40
AMBIENT
30
20
10
0
10
20 0.1
1
10
100
1000
FREQUENCY (MHz)
EVAL-8334 F08
Figure 8. EVAL-LT8334-AZ CISPR25 Radiated EMI Average Performance with 12VIN to 12VOUT at 2A, JP1 = BURST+SSFM
PEAK RE (dBµV/m)
PEAK CE (dBµV)
80
CLASS 5 PEAK LIMIT
70
EVAL-LT8334-AZ
60
EVAL-LT8334-AZ + SHIELD AMBIENT
50
40
30
20
10
0
10
20 0.1
1
10
FREQUENCY (MHz)
108
EVAL-8334 F07
Figure 7. EVAL-LT8334-AZ CISPR25 Voltage Conducted EMI Peak Performance with 12VIN to 12VOUT at 2A, JP1 = BURST+SSFM
60
50
40
30
20
10
0 10 20
0.1
CLASS 5 PEAK LIMIT EVAL-LT8334-AZ EVAL-LT8334-AZ + SHIELD AMBIENT
1
10
100
1000
FREQUENCY (MHz)
EVAL-8334 F09
Figure 9. EVAL-LT8334-AZ CISPR25 Radiated EMI Peak Performance with 12VIN to 12VOUT at 2A, JP1 = BURST+SSFM
AVERAGE CE (dBµA)
60
50
CLASS 5 AVERAGE LIMIT
EVAL-LT8334-AZ
40
EVAL-LT8334-AZ + SHIELD
30
AMBIENT
20
10
0
10
20
30
40
50
60 0.1
1
10
FREQUENCY (MHz)
100
300
EVAL-8334 F10
Figure 10. EVAL-LT8334-AZ CISPR25 Current Conducted EMI Average Performance with 12VIN to 12VOUT at 2A, JP1 = BURST+SSFM
6
PEAK CE (dBµA)
60 50 40 30 20 10 0 10 20 30 40 50 60
0.1
CLASS 5 PEAK LIMIT EVAL-LT8334-AZ EVAL-LT8334-AZ + SHIELD AMBIENT
1
10
FREQUENCY (MHz)
100
300
EVAL-8334 F11
Figure 11. EVAL-LT8334-AZ CISPR25 Current Conducted EMI Peak Performance with 12VIN to 12VOUT at 2A, JP1 = BURST+SSFM
Rev. 0
DEMO MANUAL EVAL-LT8334-AZ
EMISSIONS SHIELD (OPTION)
For the ultimate lowest emissions, an EMI shield can be attached to EVAL-LT8334-AZ. The PCB was fabricated with placeholders for five shield clips which can hold a 32mm × 32mm metal shield. Part numbers for an example shield are provided in the Parts List section in the
Hardware list. The top silkscreen picture (Figure 12) shows the placeholders for the eight surface mount shield clips. Then the emissions of the board can be tested with and without the removable clip-shield.
Figure 12. EMI Shield Clips Can Be Soldered to the Five Placeholders on the PCB, a Square 32mm × 32mm Outline Shows Where the EMI Shield Fits onto the PCB
Rev. 0
7
DEMO MANUAL EVAL-LT8334-AZ
PARTS LIST
ITEM QTY REFERENCE
Required Electrical Components
1
1 C5
2
3 C11, C17, C18
3
1 C3
4
1 C4
5
1 C6
6
1 C7
7
1 C8
8
1 C9
9
1 D1
10
1 L1
11
1 R1
12
1 R2
13
2 R3, R6
14
1 R4
15
1 R7
16
1 U1
Optional Low EMI Components
1
2 C1, C2
2
3 C10, C12, C13
3
1 C14
4
1 C16
5
1 FB1
6
1 FB2
Optional Electrical Components
1
0 C15
2
1 R5
3
1 R8
4
0 R9, R10
Hardware: For Evaluation Circuit Only
1
7 E1, E2, E3, E4, E5, E6, E7
2
1 JP1
3
0 CL1CL5
4
0 SH1
PART DESCRIPTION
CAP. CER 0.1F 50V 10% X7R 0402 AEC-Q200 CAP. CER 22F 25V 20% X5R 0805 AEC-Q200 CAP. CER 0.1F 25V 10% X7R 0402 AEC-Q200 CAP. CER 10F 50V 20% X5R 1206 AEC-Q200 CAP. CER 4.7F 50V 10% X5R 0805 AEC-Q200 LOW ESR CAP. CER 1000pF 10V 10% X7R 0402 CAP. CER 1F 25V 10% X5R 0402 AEC-Q200 CAP. CER 4.7pF 0.25pF 50V C0G 0402 AEC-Q200 DIODE LOW VF MEGA SCHOTTKY BARR RECT IND. POWER SHIELDED DRUM CORE 1.986H/7.944H 20% 100kHz 4.66A/2.33A 0.013/0.0521 DCR RES. SMD 1.15M 1% 1/16W 0402 AEC-Q200 RES. SMD 20k 1% 1/10W 0402 AEC-Q200 RES. SMD 1M 1% 1/10W 0402 AEC-Q200 RES. SMD 22k 1% 1/10W 0402 AEC-Q200 RES. SMD 154k 1% 1/10W 0402 AEC-Q200 IC-ADI LOW IQ BOOST/SEPIC/INVERTING CONVERTER WITH 5A 40V SWITCH
CAP. CER 0.1F 50V 10% X7R 0402 AEC-Q200 CAP. CER 2.2F 25V 10% X5R 0402 AEC-Q200 CAP. CER 1F 25V 10% X7R 0603 AEC-Q200 CAP. ALUM ELECT 68F 35V 20% 6.3mm × 7.7mm AEC-Q200 280mA 2000H IND. FERRITE BEAD MULTI-LAYER 880 25% 100MHz 4A 0.035 1812 AEC-Q200 IND. CHIP FERRITE BEAD, 0.05 DCR, 3A
CAP., OPTION, 0402 RES SMD 0 JUMPER 1/10W 0402 AEC-Q200 RES SMD 100k 1% 1/10W 0402 AEC-Q200 RES., OPTION, 0402
CONN-PCB SOLDER TERMINAL TURRETS CONN-PCB 10-POS MALE HDR UNSHROUDED DOUBLE ROW ST, 2mm PITCH, 4mm POST HEIGHT, 2.6mm SOLDER TAIL FIVE EMI SHIELD CLIPS EMI SHIELD 32mm × 32mm
MANUFACTURER/PART NUMBER
MURATA, GCM155R71H104KE02D MURATA, GRT21BR61E226ME13L TAIYO YUDEN, TMK105B7104KVHF MURATA, GRT31CR61H106ME01L TDK, CGA4J3X5R1H475K125AB KEMET, C0402S102K8RACAUTO MURATA, GRT155R61E105KE01D MURATA, GCM1555C1H4R7CA16D NXP SEMICONDUCTORS, PMEG4030ER, 115 EATON, DRQ74-2R2-R
VISHAY, CRCW04021M15FKED PANASONIC, ERJ-2RKF2002X PANASONIC, ERJ-2RKF1004X PANASONIC, ERJ-2RKF2202X PANASONIC, ERJ-2RKF1543X ANALOG DEVICES, LT8334RDE#PBF
MURATA, GCM155R71H104KE02D MURATA, GRT155R61E225KE13D MURATA, GRT188R71E105KE13D PANASONIC, EEE-FK1V680XP
WURTH ELEKTRONIK, 74279252
WURTH ELEKTRONIK, 742792515
PANASONIC, ERJ-2GE0R00X PANASONIC, ERJ-2RKF1003X
MILL-MAX, 2501-2-00-80-00-00-07-0 MOLEX, 87758-1016
WURTH, 36900000 WURTH, 36906326S
Rev. 0
8
SCHEMATIC DIAGRAM
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
VIN
E1
3V-26V 1
E2
GND 1
FB1 74279252
C1 0.1UF 50V
C2 P 500.V1UFN
C16 68UF 35V EEE-FK1V680XP
C4 10uF 50V 1206
R3 1MEG
E3
EN/UVLO 1
1 E4
SYNC
R8 INTVCC 100K
JP1
1
2
3
4
[] 5
6
7
8
9
10
87758-1016
E5
GND 1
SYNC BURST BURST+SSFM PULSE-SKIP PULSE-SKIP+SSFM
R1 1.15MEG
C3 0.1uF
43 21
L1 2.2uH
DRQ74-2R2-R
D1 PMEG4030ER,115
AC
C6 4.7uF
50V 0805
C10 2.2UF 25V
C11 22uF 25V 0805
C17 22uF 25V 0805
VOUT
C18 22uF 25V 0805
FB2 742792515
1
2
C12 2.2UF 25V
C13 2.2UF 25V
E6
1
C14
1uF
25V 0603
E7
1
VOUT *
12V 2A
GND
R10 DNI
C5
0.1UF
50V 3
11 12
U1
VIN SW1 SW2
2
EN/UVLO
5
BIAS
BIAS
TP1
1
R5
0
10 SYNC/MODE
9 SS
8 RT
7 FBX INTVCC 4 INTVCC
6 VC
GND NC
PAD 1 LT8334RDE
C15
R2
DNI
20.0K
2MHz
R4 22K
C7 1000pF
R6 1MEG
C8 1UF
R9 DNI C9 4.7pF
R7 154K
VOUT
* SEE USER GUIDE FOR MAX IOUT VS VIN
DEMO MANUAL EVAL-LT8334-AZ
NOTES: UNLESS OTHERWISE SPECIFIED ALL RESISTORS ARE 0402 ALL CAPACITORS ARE 0402
Rev. 0
9
DEMO MANUAL EVAL-LT8334-AZ
ESD Caution ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.
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