List of figures

AN2798

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List of figures

Figure 1.

PM6670AS demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 2.

PM6670AS demonstration board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 3.

Topside component placement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 4.

Topside view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 5.

Layer 2 view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 6.

Layer 3 view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 7.

Bottomside view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 8.

Bottomside component placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 9.

JP3 (MODE) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 10.

JP1 (DDRSEL) setting (change to “non-audible” in graphic) . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 11.

JP2 (DSCG) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 12.

JP5 (COMP) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 13.

PM6670AS test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 14.

VDDQ soft-start at 180 mW load, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 15.

VTT turn-on (S0), pulse-skip mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 16.

VDDQ = 1.8 V, VIN = 24 V, IVDDQ = 0 A, forced PWM mode. . . . . . . . . . . . . . . . . . . . . . 19

Figure 17.

VDDQ = 1.8 V, VIN = 24 V, IVDDQ = 0 A, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 18.

VDDQ = 1.8 V, VIN = 24 V, no load, non-audible pulse-skip mode (33 kHz) . . . . . . . . . . . 20

Figure 19.

VDDQ load regulation - VIN = 24 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 20.

VTT load regulation - LDOIN = VDDQ (VDDQ in forced PWM mode) . . . . . . . . . . . . . . . . 21

Figure 21.

VTTREF load regulation (VDDQ in forced PWM mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 22.

VDDQ load transient (VIN = 24 V, LOAD = 0 A to 8 A at 2.5 A/µs) (pulse-skip mode). . . . 22

Figure 23.

VTT load transient (VIN = 24 V, LOAD = – 2 A to 2 A at 2.5 A/µs) (pulse-skip mode) . . . . 22

Figure 24.

Forced PWM (blue), non-audible pulse-skip (green), pulse-skip (red) VDDQ efficiency vs. .

output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 25.

External MOS gate signals (VIN = 24 V, LOAD = 0 A) (pulse-skip mode) . . . . . . . . . . . . . 23

Figure 26.

External MOS gate signals (VIN = 24 V, LOAD = 8 A) (pulse-skip mode) . . . . . . . . . . . . . 24

Figure 27.

VDDQ, VTTREF, VTT output voltages and LDO input current, tracking discharge,

no load on any rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 28.

VDDQ, VTTREF and VTT, non-tracking discharge, no load on any output . . . . . . . . . . . . 25

Figure 29.

UV protection, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 30.

OV protection, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 31.

VDDQ, VTT, VTTREF and inductor current, thermal shutdown, pulse-skip mode . . . . . . . 28

Figure 32.

VDDQ current limit protection during a load transient (0 A to 10 A at 2.5 A/µs) . . . . . . . . . 29

Figure 33.

VTT current limit during an output short . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 34.

Switching frequency vs. input voltage, VDDQ = 1.8 V, IVDDQ = 4 A, forced PWM mode . 31

Figure 35.

Forced PWM (blue), non-audible pulse-skip (green) and pulse-skip (red), switching

frequency vs. output current, VDDQ = 1.8 V, VIN = 24 V . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 36.

IVTT = 0 A, average IC temperature = 37.5 °C, max internal IC temperature = 40.1 °C . . 33

Figure 37.

IVTT = 0.5 A, average IC temperature = 48.8 °C, max internal IC temperature = 54.3 °C. 34

Figure 38.

IVTT = 1 A, average IC temperature = 60.5 °C, max internal IC temperature = 72.7 °C . . 35

Figure 39.

IVTT = 1.5 A, average IC temperature = 73.8 °C, max internal IC temperature = 95.6 °C. 36