NCV881930-GEVB1 NCV881930 DualFET Evaluation Board User's Manual

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NCV881930 DualFET Evaluation Board User's Manual

NCV881930 Low Quiescent Current 410 kHz Automotive Synchronous Buck Controller SMD Evaluation Board for Existing or New PCB Designs

Purpose

This document describes the use and applications for the NCV881930 DualFET EVB. The EVB is designed on a four layer PCB and includes the NCV881930MW00R2G controller, NVMFD5C478NLWFT1G 40 V Dual N−Channel FET and all the necessary circuitry for an automotive synchronous buck converter. It provides 5.0 V @ 6.0 A on the output and has an input voltage range of 6.0 to 16.0 V, with capability to withstand peaks up to 40 V.

NCV881930 Description

The NCV881930 is a 410 kHz fixed−frequency low quiescent current buck controller with spread spectrum that operates up to 38 V (typical). It may be synchronized to a clock or to separate NCV881930. Peak current mode control is employed for fast transient response and tight regulation over wide input voltage and output load ranges. Feedback compensation is internal to the device, permitting design simplification. The NCV881930 is capable of converting from an automotive input voltage range of 3.5 V (4.5 V during startup) to 18 V at a constant base switching frequency. Under load dump conditions up to 45 V the regulator shuts down. A high voltage bias regulator with automatic switchover to an external 5 V bias supply is used for improved efficiency. Several protection features such as UVLO, current limit, short circuit protection, and thermal shutdown are provided. High switching frequency produces low output voltage ripple even when using small inductor values and an all−ceramic output filter capacitor, forming a space−efficient switching solution.

(2 MHz version offered with NCV891930)

EVAL BOARD USER’S MANUAL

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Figure 1. Board Photo

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Figure 2. NCV881930 Simplified Block Diagram S

R Q

OSC Q

24

BANDGAP SLOPE

COMP

VDRV BST

Current Limit

MIN ON TIME

NON OVERLAP

SYNCI FB

PWMOUT 18 VDRV 19

VCCEXT

EN 6

VNCL

VPCL SYNC0 13

12 SYNCI

8

ROSC 22 VSW

23 GH

20 PGND 21 GL 14

V_SO 16 DBIAS

V_CS 1

2 CSP 3 CSN 4 VOUT

15 VSEL 17

VIN

10 GND 9

SSC

11 RSTB Z

*

VCOMP + FB

∑

TSD OVSD UVLO

FAULT SOFTSTART VREF

RSTB CSA PWM/

PULSE SKIP 5 V LDO ^LDO

BYPASS

INTERNAL RAILS

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V_CS1

CSP2 CSN3 VOUT4 NC5

EN6 ROSC8NC7

SSC9 GND10

RSTB11

SYNCI12

SYNCO13 V_SO14

VSEL15 DBIAS16

VIN17 VDRV18

VCCEXT19 PGND20

GL21

VSW22

GH23

BST24

EPAD 25

U1 NCV881930 GNDGNDGND

openR13 GND

0.1μFC20 GND

0.1μFC19 GND

0.1μFC18 GND

VOUT

1 2 3

J3 SYNCI

SYNCI GND * High: 5.0V Output Voltage * Low/Open: 3.3V Output Voltage

VSEL

* High: Continuous Synchronous Mode * Low: Low Iq Mode * Ext. Sync. Input

SYNCI

1 2 3

J2 EN GND EN

* High: On * Low: Off

EN TP5

VINDBIAS DBIAS 2.2V

10.0k

R11

10.0kR8 TP6 1μFC21 GND^5.0V

0.1μFC22 GND

1μFC23 GND

10.0R10 0R12

TP7TP8

VOUT

0

R1 0R6 GNDGNDGND

0.012

R2 GND

0.1μFC12

4.7μF 50V

C6 GND

0.1μFC3 GNDGND

4.7μF 50V

C1 GND

4.7μF 50V

C2 0.1μFC4 0.1μFC5 GND 1μFC15 GND

VIN

VIN 1.00R3

TP3 TP4 GND

TP1 TP2 GND

VIN GND VOUT GND

Input 6 .. 16V, 40V peak Output 5.0V @ 6.0A fswitch = 410 kHz

* Input Capacitance: 3.0A rms * High−Side FET: 6.9A peak, 5.5A rms

Current Stress (6 .. 16V input) * Low−Side FET: 6.9A peak, 5.0A rms * Inductor: 6.9A peak, 6.0A rms * Output Capacitance: 0.5A rms

0.1μF

C8

GND

1μHL1 VOUT

Separate Traces!

120μF 6.3V

C9 GND

22μF 16V

C10VOUT GND

D1 NR

VTS260ESFT1G

150μF 35V

C7

1 2

J1 12

J4 TP9 GND

2

1 7,8

Q1A NVMFD5C

478NL

4

3 5,6

Q1B NVMFD5C

478NL 332R7 332R9100pFC17

4.7μHL2 0.012

R4 470pFC165.6R5

Figure 4. NCV881930−GEVB1 Schematic

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Table 1. NCV881930−GEVB1 BILL OF MATERIALS

C1, C2, C6 3 4.7 mF GCM32ER71H475KA55 MuRata CAP, CERM, 4.7 mF, 50 V,+/− 10%,

X7R, 1210 1210

C3, C4, C5, C8, C12, C18, C19, C20, C22

9 0.1 mF GCM155R71H104KE02D MuRata CAP, CERM, 0.1 mF, 50 V,+/− 10%,

X7R, AEC−Q200 Grade 1, 0402 0402

C7 1 150 mF GYA1V151MCQ1GS Nichicon CAP, Hybrid Polymer, 150 mF, 35 V, +/−

20%, 0.027 ohm, SMD D8xL10mm

C9 1 120 mF PCJ0J121MCL1GS Nichicon CAP, Aluminum Polymer, 120 mF, 6.3

V, +/− 20%, 0.024 ohm, SMD D5.0xL6.0mm

C10 1 22 mF GCM32ER71C226KE19L MuRata CAP, CERM, 22 mF, 16 V,+/− 10%,

X7R, 1210 1210

C15 1 1 mF GCM21BR71H105KA03 MuRata CAP, CERM, 1 mF, 50 V,+/− 10%, X7R,

0805

C16 1 470 pF GCM155R71H471KA37D MuRata CAP, CERM, 470 pF, 50 V,+/− 10%,

X7R, AEC−Q200 Grade 1, 0402 0402

C17 1 5.6 GCM1555C1H101JA16 MuRata CAP, CERM, 100 pF, 50 V,+/− 5%,

C0G/NP0, 0402

0402

C21, C23 2 1 mF GCM188R71E105KA64D MuRata CAP, CERM, 1 mF, 25 V,+/− 10%,

X7R, AEC−Q200 Grade 1, 0603 0603 D1 1 60 V NRVTS260ESFT1G ON Semiconductor Diode, Schottky, 60 V, 2 A, AEC−

Q101, SOD−123FL SOD−123FL

FID1, FID2,

FID3 3 N/A N/A Fiducial mark. There is nothing to buy

or mount. N/A

J1, J4 2 ED555/2DS On−Share

Technology Terminal Block, 3.5mm Pitch, 2x1, TH 7.0 x 8.2 x 6.5 mm

J2, J3 2 61300311121 Wurth Elektronik Header, 2.54 mm, 3x1, Gold, TH Header, 2.54 mm,

3x1, TH

L1 1 1 mH XAL7030−102MEB Coilcraft Inductor, Shielded, Composite, 1 mH,

21.8 A, 0.00455 ohm, SMD 7.5x7.5x3.1 mm L2 1 4.7 mH XAL7070−472MEB Coilcraft Inductor, Shielded, Composite, 4.7 mH,

13.6 A, 0.01 W, SMD

7.2x7x7.5 mm

Q1 1 40 V NVMFD5C478NLWFT1G ON Semiconductor MOSFET, 2−CH, N−CH, 40 V, 29 A,

DFN8 5x6 DFN8, 5x6

R1, R6, R12 3 0 CRCW06030000Z0EA Vishay−Dale RES, 0,5%, 0.1 W, 0603 0603

R2, R4 2 0.012 ERJ−8CWFR012V Panasonic RES, 0.012, 1%, 1 W, AEC−Q200

Grade 0, 1206 1206

R3 1 1.00 CRCW06031R00FKEA Vishay−Dale RES, 1.00, 1%, 0.1 W, 0603 0603

R5 1 5.6 CRCW12065R60JNEA Vishay−Dale RES, 5.6, 5%, 0.25 W, 1206 1206

R7, R9 2 332 CRCW0603332RFKEA Vishay−Dale RES, 332, 1%, 0.1 W, 0603 0603

R8, R11, R13 3 10.0 k CRCW060310K0FKEA Vishay−Dale RES, 10.0 k, 1%, 0.1 W, 0603 0603

R10 1 10.0 CRCW060310R0FKEA Vishay−Dale RES, 10.0, 1%, 0.1 W, 0603 0603

TP1, TP3 2 5000 Keystone Test Point, Miniature, Red, TH Red Miniature

Testpoint

TP2, TP4, TP9 3 5001 Keystone Test Point, Miniature, Black, TH Black Miniature

Testpoint TP5, TP6, TP7,

TP8 4 5002 Keystone Test Point, Miniature, White, TH White Miniature

Testpoint U1 1 NCV881930MW00R2G ON Semiconductor Low Quiescent Current 410 kHz Auto-

motive Synchronous Buck Controller

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PBC ASSEMBLY AND LAYERS

Figure 5 and Figure 6 shows the top and bottom assembly and the four−layers of the PCB. The PCB is 47 mm x 44 mm (length x width) where the height of the PCB is approximately 11 mm

Figure 5. NCV881930−GEVB1 Top, Bottom Layer

Figure 6. NCV881930−GEVB1 Inner1, Inner2 Layer

Connectors

There are 2 screw terminals and 2 pin headers described in Table 2 below. The source and load are connected by the screw terminals and the pin headers are used to set different modes of operation.

All signals are referenced to a common ground.

The buck converter is enabled and disabled by plugging a jumper on the corresponding pins of pin header J2. Pin

header J3 can be used to feed in an external synchronization signal (J3.2, check datasheet for electrical specification). If this feature is not used, a jumper is needed to set the mode of operation to either continuous synchronous operating mode or low Iq mode.

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Table 2. CONNECTOR DESCRIPTIONS

Ref Def Name I/O Type Description Value [V]

J1.1 VIN Power Screw Terminal Ground (Power Input) 0 V

J1.2 GND Power Screw Terminal Power Input 6.0 .. 16.0 V

J2.1 VIN Output Pin Header Logic High 6.0 .. 16.0 V

J2.2 EN Input Pin Header Enable Input

Low: Disabled High: Enabled

Low: < 0.8 V High: > 1.4 V

J2.3 GND Output Pin Header Logic Low 0 V

J3.1 DBIAS Output Pin Header Logic High 2.0 .. 2.4 V

J3.2 SYNCI Input Pin Header Select mode / ext. Sync.

Low: Low Iq Mode High: Continuous Sync. Mode

Low: < 0.8 V High: > 2.0 V

J3.3 GND Output Pin Header Logic Low 0 V

J4.1 GND Power Screw Terminal Ground (Power Output) 0 V

J4.2 VOUT Power Screw Terminal Power Output 5.0 V (3.3 V)

INITIAL OPERATION

Hook up and initial operation of the board is straight forward.

1. Use a lab power supply with an output current capability of at least 6.0 A. Set the output voltage to 12.0 V, switch it off/disable it and connect it to screw terminal J1.

(J1.1: Positive, J1.2: GND)

2. Connect an electronic load capable to handle at least 5.0 V and 6.0 A to screw terminal J4. Set the load to 0 A.

(J4.2: Positive, J4.1: GND)

3. Put a jumper on pin header J2 to short pins 1 (VIN) and 2 (EN). This will enable the controller as soon as the supply voltage is applied.

4. Put a jumper on pin header J3 either on pin 1 (DBIAS) and 2 (SYNCI) for continuous synchronous mode or on pins 2 (DBIAS) and 3 (GND) for low Iq mode.

5. After checking all cabling and jumper settings, switch on/enable the power supply and verify that

the output voltage of the board is 5.0 V. If not, check again all connections and jumper settings.

6. If the output voltage is 5.0 V, the board is working properly and the load can be increased and further measurements done.

Output Voltage

NCV881930 has two fixed output voltage options, 3.3 V and 5.0 V. By pulling pin VSEL to DBIAS by a 10 kW resistor, the output voltage is set to 5.0 V. Leaving VSEL floating or connecting to GND, the output voltage is set to 3.3 V.

Dependent on the output current, a modification of the power stage (inductor, shunt, output capacitance) might be necessary. Please consult therefore Table 6 in the datasheet.

Efficiency

The efficiency for continuous synchronous mode is shown in Figure 7. This measurement doesn’t take into account losses of the input filter (inductor L1).

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Figure 7. Efficiency for 8.0, 12.0 and 16.0 V Input Voltage

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Thermal Image

The thermal images show the circuit at an ambient temperature of 21°C with an input voltage of 12.0 V, 3.0 A (Figure 8) and 6.0 A (Figure 9) load.

3.0 A load

♦ FET Q1: 51 °C

♦ Inductor L2: 49 °C 6.0 A load

♦ FET Q1: 110 °C

♦ Inductor L2: 101 °C

Figure 8. Thermal Image at 3.0 A Load

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Figure 9. Thermal Image at 6.0 A Load

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Transient Response

The response to a load step from 3.0 A to 6.0 A and vice versa at 12.0 V input voltage is shown in Figure 10.

Channel 1

♦ Output current, load step 3.0 to 6.0 A

♦ 2 A/div, 1 ms/div Channel 2

♦ Output voltage, −143 mV (−2.9%) undershoot, +140 mV (2.8%) overshoot

♦ 100 mV/div, 1 ms/div, AC coupled

Figure 10. Transient Response on 3.0 A Load Step

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Frequency Response

The frequency response at 12.0 V input voltage and 6.0 A load is shown in Figure 11.

Trace 1

♦ 19.7 kHz bandwidth

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Figure 11. Frequency Response at 6.0 A Load

Impact of output capacitance configuration on performance The datasheet of NCV881930 gives detailed recommendations for the output filter configuration (inductance, shunt resistance, output capacitance) dependent on the output voltage and current. A detailed test series with different output capacitance configurations showed, that different configurations are possible without decreasing performance or causing stability issues.

Table 3 shows the measurement results for various output capacitor configurations and their corresponding performance regarding ripple, transient response and phase/gain margin.

Output capacitor configuration

Different sets of high capacitance ceramic and polymer capacitors were used for the measurements.

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1x 100 nF, 50 V, 0603, X7R, always populated muRata GCJ188R71H104KA12D

•

²²mF ceramic, 16 V, 1210, X7R muRata GCM32ER71C226ME19L 18 mF @ 5.0 V DC, 2 mW ESR @ 410 kHz

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100 mF polymer

Nichicon PCJ0J101MCL1GS 24 mW ESR @ 100 kHz

•

¹²⁰mF polymer

•

²²⁰mF polymer

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Table 3. OUTPUT RIPPLE, TRANSIENT RESPONSE & FREQUENCY RESPONSE MEASUREMENTS

Polymer: 220 mF, 6.3 V 1 1 1 1 # of caps

Ceramic: 22 mF, 16 V 0 1 2 3 # of caps

Output Ripple, peak−peak 31 20 9 4 [mV]

Output Ripple, peak−peak 0.6 0.4 0.2 0.1 [%]

Transient Response, peak−peak 315 305 285 285 [mV]

Transient Response, peak 158 153 143 143 [mV]

3.2 3.1 2.9 2.9 [%]

Bandwidth 10.6 9.8 9.0 9.2 [kHz]

Phase Margin 84 82 79 79 [deg]

Gain margin −24 −21 −21 −21 [dB]

3.4 3.2 3.2 3.1 [%]

Bandwidth 23.9 19.7 16.4 15.0 [kHz]

Gain margin −23 −19 −20 −21 [dB]

3.5 3.4 3.1 3.2 [%]

Bandwidth 22.7 18.8 17.3 15.8 [kHz]

Gain margin −23 −20 −20 −20 [dB]

3.4 3.3 3.3 3.3 [%]

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Outcome

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Even with only a polymer capacitor the output voltage ripple is well below 1 % of the output voltage (max. is 31 mV which equals 0.6 %).

If one or more high capacitance ceramic capacitors are added, the ripple voltage decreases significantly.

Roughly by a factor of two for each additional 22 mF ceramic capacitor.

If only ceramic capacitors are used, the voltage ripple is in the single digit range.

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The phase and gain margin show very good values over a broad range of output capacitance and is independent of the type of capacitor (ceramic, polymer or a mix).

Basically any value between 54 mF (3x 22 mF ceramic taking DC−biasing into account) and 274 mF (1x

220mF polymer + 3x 22 mF ceramic) can be used.

Even higher output capacitance should be no problem, lower capacitance will degrade phase and gain margin too much.

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The transient response is almost identical for all measurements and independent of the output capacitance. The voltage drop / overshoot is between 143 mV (2.9 %) and 173 mV (3.5 %).

With low output capacitance the bandwidth increases and with higher output capacitance it decreases.

Therefore a lower bandwidth is compensated by larger capacitance and vice versa.

As the device is internally compensated, the reason for that behavior is the shift of the load pole:

f_PoleLoad+ 1

2 p C_out R_load+ 1

2 p C_out V_out I_out

(eq. 1)

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