ST AN2566 APPLICATION NOTE

AN2566

Application note

PM6680 evaluation kit dual step-down controller with auxiliary voltages for notebook power system

Introduction

PM6680A evaluation kit order code: STEVAL-ISA053V1.

The PM6680 is a dual step-down controller with adjustable output voltages for notebook computer power systems. The PM6680 evaluation kit is designed to test the performance of the PM6680 by employing a typical application circuit that allows testing of all PM6680 device functions. The kit features two switching sections, with (typically) 1.5 V and 1.05 V outputs, from a 6 V to 28 V input battery voltage. The operating switching frequency of the two switching sections is 200 kHz / 300 kHz, respectively. Each switching section delivers more than 5 A output current. Moreover, an internal linear regulator can provide 5 V @ 100 mA peak current.

Figure 1. PM6680 evaluation kit

Top	Bottom

April 2008

Rev 3

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www.st.com

Contents	AN2566

Contents

1	Main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 5
2	Evaluation kit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		6
3	Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		7
4	Evaluation board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		9
5	I/O interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		11
6	Recommended equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		12
7	Quick start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		13
8	Jumper settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		14
9	Feedback output connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		16
10	Test setup and performance summary . . . . . . . . . . . . . . . . . . . . . . . . .		17
	10.1	Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	10.2	Power-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	10.3	Soft-start and shutdown waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
	10.4	1.5 V and 1.05 V output efficiency vs. load current . . . . . . . . . . . . . . . . .	19
	10.5	Power consumption analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20
	10.6	Switching frequency vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . .	23
	10.7	Linear regulator output voltages vs. output current . . . . . . . . . . . . . . . . .	24
	10.8	Load transient responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	24
11	Representatives waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		26
12	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		28

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AN2566	List of figures

List of figures

Figure 1. PM6680 evaluation kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Figure 2. Evaluation kit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 3. PM6680 evaluation board layout - top layer (PGND plain and component side) . . . . . . . . . 9 Figure 4. PM6680 evaluation board layout - inner layer 1 (SGND layer and VIN plane) . . . . . . . . . . . 9 Figure 5. PM6680 evaluation board layout - inner layer 2 (SGND layer and signals) . . . . . . . . . . . . 10 Figure 6. PM6680 evaluation board layout - bottom layer (PM6680 and component side) . . . . . . . . 10 Figure 7. REF and LDO5 power-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 8. Section 1 soft-start waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 9. Section 2 soft-start waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 10. Section 1 shutdown waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 11. Section 2 shutdown waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 12. 1.5 V SMPS efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 13. 1.05 V SMPS efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 14. Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 15. Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 16. Input current vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 17. Device current consumption vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 18. Device current consumption vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 19. 1.5 V output switching frequency vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 20. 1.05 V output switching frequency vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 21. LDO5 output vs. load current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 22. SMPS 1.5 V load transient response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Figure 23. SMPS 1.05 V load transient response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Figure 24. SMPS pulse skip mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Figure 25. SMPS no-audible skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Figure 26. SMPS PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

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List of tables	AN2566

List of tables

Table 1. Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 2. The test points of the evaluation board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Table 3. Jumper S11 - V5SW pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table 4. Jumper S3 - FSEL pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table 5. Jumper S10 - SKIP pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Table 6. Jumper S4, S5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table 7. Jumper S8, S9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table 8. Jumper S4, S5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table 9. Jumper S8, S9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Table 10. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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AN2566	Main features

1Main features

●Constant on-time control allows very fast load transients

●6 V to 28 V input voltage range

●5 V auxiliary output voltage

●Adjustable switching outputs

●Lossless current sensing using low side MOSFET RDS(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 (5 V / 3 V selectable switching frequency)

●Selectable pulse skip and no-audible skip modes at light loads

●Independent power good signals

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Evaluation kit schematic	AN2566

2 Evaluation kit schematic

Figure 2. Evaluation kit schematic

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AN2566	Component list

3 Component list

	Table 1.	Component list
	Name	Description	Size	Value	Supplier	Part number
	C1, C2,	Ceramic capacitor	1210	10 µF	Taiyo Yuden	UMK325BJ106KM
	C3	50 V
	C4	Ceramic capacitor	1210	Not installed
		50 V
	C5, C6	Ceramic capacitor	0805	0,1 µF	Standard
	C7	Low ESR capacitor	D case	Not installed	Standard
	C8	Low ESR capacitor	D case	330 µF	POSCAP - Sanyo	4TPD33OM
		4 V, 12 mΩESR
	C11	Low ESR capacitor	D case	Not installed	Standard
	C12	Low ESR capacitor	D case	330 µF	POSCAP - Sanyo	4TPD33OM
		4 V, 12 mΩESR
	C13, C14	Ceramic capacitor	0805	5.6 nF	Standard
	C15, C16	Ceramic capacitor	0603	1 nF	Standard
	C17, C18	Ceramic capacitor	0603	47 pF	Standard
	C19	Ceramic capacitor	0805	0.1 µF	Standard	B37941K5104K62
		50 V
	C26	Tantalum capacitor	C case	4.7 µF	AVX TPS	TPSC475*035#0600
		35 V
	C20	Ceramic capacitor	0603	1 µF	Standard
	C21	Tantalum capacitor	B case	4.7 µF	AVX THJ	THJB475*016#JN
		package A, 16 V
	C22	Ceramic capacitor	0805	220 nF	Standard
	C9, C10	Ceramic capacitor	0805	Not installed	Standard
	C23	Ceramic capacitor	0603	10 pF	Standard
	CIN	Electrolytic capacitor	D 10 mm	Not installed	Sanyo	25SVPD39M
		39 µF, 25 V
	CREF	Ceramic capacitor	0603	100 nF	Standard
	C24,C25	Ceramic capacitor	0805	10 µF	Standard
	C27	Ceramic capacitor	0805	Not installed	Standard
	C28	Tantalum capacitor	3216	Not installed	Standard
	D1	Dual Schottky diode	SOT23		STMicroelectronics	BAT54A
	D2,D3	Diode 1 A, 30 V	DO216-AA		STMicroelectronics	STPS1L30M
	IC1	PM6680 device	VFQFPN-32		STMicroelectronics	PM6680
			5 mm x 5 mm

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Component list					AN2566
Table 1.	Component list (continued)
Name	Description	Size	Value	Supplier	Part number
L1	1.5 µH inductor, 12 A	13 mm x	1.5 µH	Coilcraft	MLC1538-152ML
	sat.	13 mm
L2	2.5 µH inductor, 8 A	13 mm x	2.5 µH	Coilcraft	MLC1550-252ML
	sat.	13 mm
M1	MOSFET control FET	SO-8		STMicroelectronics	STS12NH3LL
	SO-8
M2	MOSFET control FET	SO-8		STMicroelectronics	STS12NH3LL
	SO-8
M3	MOSFET Sync FET	SO-8		STMicroelectronics	STS12NH3LL
	SO-8
M4	MOSFET Sync FET	SO-8		STMicroelectronics	STS12NH3LL
	SO-8
R7,R8	Resistor	0805	680 Ω	Standard
R3	Resistor	0805	22 kΩ	Standard
R4	Resistor	0805	36 kΩ	Standard
R5	Resistor	0805	3.3 kΩ	Standard
R6	Resistor	0805	3 kΩ	Standard
R24	Resistor	0805	1.1 kΩ	Standard
R25	Resistor	0805	820 Ω	Standard
R9	Resistor	0805	47 Ω	Standard
R10,R11	Resistor	0805	10 Ω	Standard
R12,R13,	Resistor	0603	100 kΩ	Standard
R14,R15
R16	Resistor	0603	150 kΩ	Standard
R18,R19	Resistor	0603	Not installed
R17	Resistor	0603	560 kΩ	Standard
R26	Resistor	1206	3.9 Ω	Standard
R20, R21,	Resistor	0805	0 Ω	Standard
R22, R23
R27	Resistor	0805	10 kΩ	Standard
R28	Resistor	0805	6.8 kΩ	Standard
R29	Resistor	0805	11 kΩ	Standard
R30	Resistor	0805	1.8 kΩ	Standard
R31	Resistor	0805	Not installed	Standard
R32	Resistor	0805	Not installed	Standard
RLD5V,	Resistor	0805	Not installed	Standard
RLD3V

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AN2566	Evaluation board layout

4 Evaluation board layout

Figure 3. PM6680 evaluation board layout - top layer (PGND plain and component side)

Figure 4. PM6680 evaluation board layout - inner layer 1 (SGND layer and VIN plane)

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