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SP6138 (3A MAX.)
TM
Evaluation Board Manual
Easy Evaluation for the SP6138ER1 12V Input, 0 to 3A Output Synchronous Buck Converter Precision 0.80V with 1% High Accuracy Reference Small form factor Feature Rich: Single supply operation, Overcurrent protection with auto-restart, Power Good Output, Enable input, Fast transient response, Supply and Output Dead Short Circuit Shutdown Protection, Programmable soft start. SP6138EB SCHEMATIC
Aug 24-06
SP6138 Evaluation Manual
(c)2006 Sipex Corporation
USING THE EVALUATION BOARD 1) Powering Up the SP6138EB Circuit Connect the SP6138 Evaluation Board with an external +12V power supply. Connect with short leads and large diameter wire directly to the "VIN" and "GIN" posts. Connect a Load between the "VO" and "GO" posts, again using short leads with large diameter wire to minimize inductance and voltage drops. 2) Measuring Output Load Characteristics It's best to ground any reference scope and digital meters using the Star GND post in the center of the board. VOUT ripple can best be seen by touching the probe tip to the pad for COUT and the scope GND collar touching the Star GND post - avoid a GND lead on the scope which will increase noise pickup. 3) Using the Evaluation Board with Different Output Voltages The SP6138 Evaluation Board has been tested and delivered with the output set to 3.30V. By simply changing one resistor, R2, the SP6138 can be set to other output voltages. The relationship in the following formula is based on a voltage divider from the output to the feedback pin VFB, which is set to an internal reference voltage of 0.80V. Standard 1% metal film resistors of surface mount size 0603 are recommended. VOUT = 0.80V ( R1 / R2 + 1 ) => R2 = R1 / [ (VOUT / 0.80V ) - 1 ] Where R1 = 68.1K and for the VOUT = 0.80V setting, simply remove R2 from the board. Furthermore, one could select the value of R1 & R2 combination to meet the exact output voltage setting by restricting R1 resistance range such that 50K R1 100K for overall system loop stability. Note that since the SP6138 Evaluation Board design was optimized for 12V down conversion to 3.30V, changes of output voltage and/or input voltage will alter performance from the data given in the Power Supply Data section. POWER SUPPLY DATA The SP6138EB is designed with an accurate 1.5% reference over line, load and temperature. Figure 1 data shows a typical SP6138ER Evaluation Board efficiency plot, with efficiencies to 86% and output currents to 3A. SP6138ER Load Regulation in Figure 2 shows only 0.09% change in output voltage step response from no load to 3A load. Figures 3 and 4 show the fast transient response of the SP6138. Start-up response in Figures 5, 6 and 7 show a controlled start-up with different output load behavior when power is applied where the input current rises smoothly as the soft-start ramp increases. In Figure 8 the hiccup mode gets activated in response to an output dead short circuit condition and will soft-start until the over-load is removed. Figures 9 and 10 show output voltage ripple less than 10mV over the complete load range. While data on individual power supply boards may vary, the capability of the SP6138ER of achieving high accuracy over a range of load conditions shown here is quite impressive and desirable for accurate power supply design.
Aug 24-06
SP6138 Evaluation Manual Page 2 of 9
(c)2006 Sipex Corporation
100 90
Efficiency vs Load Current
Output Voltage (V)
3.36
Output Voltage vs Load Current
Efficiency (%)
80 70 60 50 40 0.0 0.5 1.0 1.5 2.0 2.5 3.0
3.35
Vin=12V Vout=3.3V
3.34
Vin=12V Vout=3.3V
0.0 0.5 1.0 1.5 2.0 2.5 3.0
3.33
Load current (A)
Load current (A)
Figure 1. Efficiency vs Load
Figure 2. Load Regulation
Vout (100mV/div)
Vout (200mV/div)
Vin=12V Vout=3.3V
Vin=12V Vout=3.3V
Iout (2A/div)
Iout (2A/div)
Figure 3. Load Step Response: 1->3A
Figure 4. Load Step Response: 0->3A
Vin Vin Vout Vout SoftStart SoftStart Iout(2A/div) Iout(2A/div)
Figure 5. Start-Up Response: No Load Load
Figure 6. Start-Up Response: 1A
Vin=12V Vout=3.3V
Vin
Vout
Vout SoftStart
SoftStart
Vin=12V Vout=3.3V
Iout(2A/div) Ichoke(10A/div)
Figure 7. Start-Up Response: 3A Load
Figure 8. Output Load Short Circuit
Aug 24-06
SP6138 Evaluation Manual Page 3 of 9
(c)2006 Sipex Corporation
Vout Ripple(10mV/div)
Vout Ripple(10mV/div)
Vin=12V Vout=3.3V
Vin=12V Vout=3.3V
SW Node
SW Node
Figure 9. Output Noise at No Load
Figure 10. Output Noise at 3A Load
Inductance (uH) 2.2
Manufacturer/Part No.
COOPER DR73-2R2
INDUCTORS - SURFACE MOUNT Inductor Specification Size Inductor Type Series R Isat mOhms (A) LxW(mm) Ht.(mm) 16.5 5.52 7.6X6.0 3.55 Shielded Ferrite Core CAPACITORS - SURFACE MOUNT Capacitor Specification Size ESR Ripple Current Voltage Capacitor ohms (max) (A) @45C LxW(mm) Ht.(mm) (V) Type 0.005 4.00 2.0x1.25 1.25 16.0 X5R Ceramic 0.005 4.00 2.0x1.25 1.25 6.3 X5R Ceramic
Manufacturer Website
www.cooperet.com
Capacitance( uF) 4.7 22
Manufacturer/Part No.
AVX 08053D475MAT AVX 08056D226MAT
Manufacturer Website
www.avx.com www.avx.com
MOSFETS - SURFACE MOUNT MOSFET Dual N-Ch Manufacturer/Part No.
VISHAY Si7214DN
RDS(on) ohms (max) 0.047
MOSFET Specification Qg ID Current Voltage Foot Print (A) nC (Typ) nC (Max) (V) 5.9 4.2 6.5 30.0 Power-PAK 1212-8
Manufacturer Website
www.vishay.com
Table 1: SP6138EB Suggested Components and Vendor Lists
Aug 24-06
SP6138 Evaluation Manual Page 4 of 9
(c)2006 Sipex Corporation
LOOP COMPENSATION DESIGN The open loop gain of the SP6138 Evaluation Board can be divided into the gain of the error amplifier GAMP(s), PWM modulator GPWM, buck converter output stage GOUT(s), and feedback resistor divider GFBK. In order to crossover at the selected frequency fco, the gain of the error amplifier must compensate for the attenuation caused by the rest of the loop at this frequency. The goal of loop compensation is to manipulate the open loop frequency response such that its gain crosses over 0dB at a slope of -20dB/dec. The open loop crossover frequency should be higher than the ESR zero of the output capacitors but less than 1/5 of the switching frequency fs to insure proper operation. Since the SP6138EB is designed with ceramic type output capacitors, a Type III compensation circuit is required to give a phase boost of 180 in order to counteract the effects of the output LC underdamped resonance double pole frequency.
Figure 11. SP6138EB Voltage Mode Control Loop with Loop Dynamic
Aug 24-06
SP6138 Evaluation Manual Page 5 of 9
(c)2006 Sipex Corporation
The simple guidelines for positioning the poles and zeros and for calculating the component values for a Type III compensation scheme are as follows:
Where ZSF=(f compensation double zero)/(f circuit double pole) Here ZSF is set at 1.2. As a particular example, consider for the following SP6138EB, 3AMAX with a type III Voltage Loop Compensation component selections: Vin_max = 15V Vout = 3.30V @ 0 to 3A load Select L = 2.2 uH => 15% current ripple. Select Cout = 22uF Ceramic capacitors (Resr 5m) fs = 2500KHz SP6138ER1 internal Oscillator Frequency Vramp_pp = 1.0V SP6138ER1 internal Ramp Peak-to-Peak Amplitude
Aug 24-06
SP6138 Evaluation Manual Page 6 of 9
(c)2006 Sipex Corporation
Step by step design procedures: a. b. c. d. e. f. g. h. R2 = 21.8 CZ3 = 85pF Let fcrsover=200KHz then: RZ2 = 60.3k CZ2 = 96pF CP1 = 1.1pF RZ3 = 0.75K CF1 = 18pF to stabilize SP6138ER1 internal Error Amplify
The above component values were used as a starting point for compensating the converter and after laboratory testing the values shown in the circuit schematic of page 1 were used for optimum operation.
Figure 12- Gain/Phase measurement of SP6138EB shown on page 1, cross-over frequency (fc) is just above 200KHz with a corresponding phase of 45 degrees
Aug 24-06
SP6138 Evaluation Manual Page 7 of 9
(c)2006 Sipex Corporation
PCB LAYOUT DRAWINGS
Figure 13. SP6138EB Component Placement
Figure 14. SP6138EB PCB Layout Top Side
Figure 15. SP6138EB PCB Layout Bottom Side
Aug 24-06
SP6138 Evaluation Manual Page 8 of 9
(c)2006 Sipex Corporation
Figure 16. SP6138EB PCB Layout Inner Layer 1 & Inner Layer 2
Line No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Ref. Des. PCB U1 MT,MB DBST L1 C1, CBST, CS CSP CI CO CVCC C5 CSS CP1 CF1 CZ2 CZ3 R1 R2 R3, R4, RS3 R5 RZ2 RZ3 RS1, RS2 J1 (J1) VIN, VOUT, VCC, GIN, GO, GND, SS, PWRGD, UVIN
Qty. 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 1 1 1
Manuf. Sipex Sipex Vishay Semi Vishay Semi COOPER Bussmann TDK TDK AVX AVX TDK TDK TDK TDK TDK TDK TDK Panasonic Panasonic Not populated Panasonic Panasonic Panasonic Panasonic Sullins Sullins
Manuf. Part Number 146-6599-00 SP6138ER1 Si7214DN SD101AWS DR73-2R2 C1005JB1C104K C1005JB1H682K 08053D475MAT 08056D226MAT C1608JF0J475Z C1005JB1E103K C1005JB1E473K C1005CH1H060D C1005CH1H180J C1005CH1H101J C1005CH1H470J ERJ-2RKF6812X ERJ-2RKF2152X ERJ-2RKF1002X ERJ-2RKF5492X ERJ-2RKF1001X ERJ-2RKF4991X PTC36SAAN STC02SYAN
Layout Size 1.175"x1.934" QFN-16 PowerPAK 1212-8 Dual SOD-323 7.6x6mm 0402 0402 0805 0805 0603 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 .32x.12 .2x.1
Component SP6138EB 2.5MHz Synchronous Buck Controller Dual NFET 30V, 47mOhm 15mA-30V Schottky Diode 2.20uH Coil 4.15A 16.5mOhm 0.1 uF Ceramic X5R 16V 6.8nF Ceramic X5R 50V 4.7uF Ceramic X5R 25V 20% 22uF Ceramic X5R 6.3V 20% 4.7uF Ceramic X5R 6.3V 0.01uF Ceramic X7R 25V 47nF Ceramic X7R 25V 6pF Ceramic COG 50V 5% 18pF Ceramic COG 50V 5% 100pF Ceramic COG 25V 5% 47pF Ceramic COG 50V 5% 68.1K Ohm Thick Film Res 1% 21.5K Ohm Thick Film Res 1% 10.0K Ohm Thick Film Res 1% 54.9K Ohm Thick Film Res 1% 1.0K Ohm Thick Film Res 1% 5.11K Ohm Thick Film Res 1% 36-Pin (3x12) Header Shunt
Vendor Phone Number 978-667-7800 978-667-7800 402-563-6866 800-344-4539 561-752-5000 978-779-3111 978-779-3111 843-448-9411 843-448-9411 978-779-3111 978-779-3111 978-779-3111 978-779-3111 978-779-3111 978-779-3111 978-779-3111 800-344-4539 800-344-4539 800-344-4539 800-344-4540 800-344-4540 800-344-4541 800-344-4539 800-344-4539
26
9
Vector Electronic
K24C/M
.042 Dia
Test Point Post
800-344-4539
Table 2: SP6138EB List of Materials
ORDERING INFORMATION Model Temperature Range Package Type SP6138EB ..............................- 40C to +85C.....................SP6138 Evaluation Board SP6138ER1............................ - 40C to +85C............................................16-pin QFN
Aug 24-06
SP6138 Evaluation Manual Page 9 of 9
(c)2006 Sipex Corporation

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