AN2815 Datasheet, PDF (4/42 Pages) STMicroelectronics – High-efficiency step-down controller

List of figures
List of figures
AN2815
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PM6675AS demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
PM6675AS demonstration board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Top side component placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Layer 2 view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Layer 3 view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Bottom view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Bottom side component placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
JP3 (VSEL) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
JP1 (NOSKIP) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
JP2 (LILIM) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
JP5 (COMP) setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
PM6675AS demonstration board test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
V_OUT soft-start at 150 mW load, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
L_OUT turn-on, V_OUT in pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
V_OUT = 1.5 V, V_IN = 24 V, I_VOUT = 0 A, forced-PWM mode . . . . . . . . . . . . . . . . . . . . . . . . 21
V_OUT = 1.5 V, V_IN = 24 V, I_VOUT = 0 A, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . 22
V_OUT = 1.5 V, V_IN = 24 V, no load, non-audible pulse-skip mode (33 kHz) . . . . . . . . . . . . 23
V_OUT load regulation - V_IN = 24 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
L_OUT load regulation - LDOIN = V_OUT , V_OUT in forced PWM mode . . . . . . . . . . . . . . . . . 25
V_OUT load transient (V_IN=24 V, LOAD=0 A to 7 A at 2.5 A/µs), pulse-skip mode. . . . . . . . 26
V_OUT load transient (V_IN = 24 V, LOAD=0 A to 7 A at 2.5 A/µs), pulse-skip mode. . . . . . . 27
Forced PWM (blue), non-audible pulse-skip (green), pulse-skip (red), efficiency vs.
output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
External MOSFET gate signals (V_IN = 24 V, LOAD = 0), pulse-skip mode . . . . . . . . . . . . 29
External MOSFET gate signals (V_IN = 24 V, LOAD = 7 A), pulse-skip mode . . . . . . . . . . 29
V_OUT and L_OUT output voltages, V_OUT soft-end, L_OUT powered by an auxiliary rail. . . . . . 30
V_OUT and L_OUT output voltages, L_OUT soft-end . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
UV protection, pulse-skip mode, L_OUT powered by an auxiliary rail . . . . . . . . . . . . . . . . . . 32
OV protection, pulse-skip mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
V_OUT and L_OUT rails, thermal shutdown, pulse-skip mode, L_OUT powered by V_OUT . . . . . 34
V_OUT current limit protection during a load transient (0 A to 9 A at 2.5 A/µs . . . . . . . . . . . 35
L_OUT current limit during an output short . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Switching frequency vs. input voltage, V_OUT = 1.5 V, I_VOUT = 2 A, forced PWM mode . . . 37
Forced PWM (blue), non-audible pulse-skip (green) and pulse-skip (red), Switching
frequency vs. output current, V_OUT = 1.5 V, V_IN = 24 V . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
I_LOUT = 0 A, average IC temperature = 31.0 °C, max internal IC temperature = 33.1 °C. . 39
I_LOUT = 0.2 A, average IC temperature = 38.2°C, max internal IC temperature = 40.7 °C . 39
I_LOUT = 0.5 A, average IC temperature = 38.2 °C, max internal IC temperature = 41.5 °C 40
I_LOUT = 1.0 A, average IC temperature = 48°C, max internal IC temperature = 55.2 °C . . 40
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