Texas Instruments TPS40090EVM-002 Closed-Loop Performance, Output Ripple and Noise, Bode Plot

SLUU195 − June 2004

6.2Closed-Loop Performance

The TPS40090 uses peak current-mode control. Figure 10 shows the bode plots at 100 A of

load current, where no droop function is implemented. The crossover frequency is at 89 kHz with phase margin of 40°.

GAIN AND PHASE

vs

OSCILLATOR FREQUENCY

	80				180
	60				135
				PHASE	90
dB	40				45
						5
−						−
Gain	20				0	Phase
	0				−45
					−90
	−20		GAIN
		VIN = 12 V
					−135
		VOUT = 1.5 V
	−40	IOUT = 10 A			−180
	100	1 k	10 k	100 k	1 M
			fOSC − Oscillator Frequency − kHz

Figure 10. Bode Plot

6.3Output Ripple and Noise

Figure 11 shows typical output noise where VIN=12 V, and IOUT=100A. The output ripple is less than 10 mV.

IOUT = 100 A

Output Voltage Ripple

(10 mV/div)

t − Time − 500 ns / div

Figure 11. Output Noise

16TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A