Maxim MAX12527 manual Grounding, Bypassing, and Board Layout

	Dual, 65Msps, 12-Bit, IF/Baseband ADC
MAX12527	3.3V
	0.1µF		3V						0.1µF	2.2µF
		1
			5
			20kΩ					REF_P	VDD
		MAX6029	1%
							0.1µF		REFOUT
		(EUK30)
										0.1µF
			20kΩ				10µF	0.1µF
		2	1%			2.413V		MAX12527
				1
				4	47Ω			REF_N
							0.1µF
				MAX4230
		0.47µF		3		330µF
				10µF
				6V	1.47kΩ	6V
			52.3kΩ					COM_	REFIN
			1%				0.1µF		GND
						1.647V
				1
				4	47Ω
				MAX4230				3.3V
				3		330µF
				10µF
			52.3kΩ	6V	1.47kΩ	6V
			1%						0.1µF	2.2µF
				1		0.880V			VDD
				4	47Ω			REF_P
			20kΩ				0.1µF		REFOUT
				MAX4230
			1%	3						0.1µF
				10µF		330µF	10µF	0.1µF
				6V		6V
					1.47kΩ			MAX12527
			20kΩ
			1%					REF_N
							0.1µF
			20kΩ
			1%
								COM_	REFIN
							0.1µF		GND

Figure 13. External Unbuffered Reference Driving Multiple ADCs

ence, allowing REF_P, REF_N, and COM_ to be driven directly by a set of external reference sources.

Figure 13 uses a MAX6029 precision 3.000V bandgap reference as a common reference for multiple convert- ers. A seven-component resistive divider chain follows the MAX6029 voltage reference. The 0.47µF capacitor along this chain creates a 10Hz LP filter. Three MAX4230 amplifiers buffer taps along this resistor chain providing 2.413V, 1.647V, and 0.880V to the MAX12527 REF_P, REF_N, and COM_ reference inputs. The feedback around the MAX4230 op amps provides additional 10Hz LP filtering. Reference volt- ages 2.413V and 0.880V set the full-scale analog input

range for the converter to ±1.022V (±[VREF_P - VREF_N] x 2/3).

Note that one single power supply for all active circuit components removes any concern regarding power- supply sequencing when powering up or down.

Grounding, Bypassing, and Board Layout

The MAX12527 requires high-speed board layout design techniques. Refer to the MAX12557 EV kit data sheet for a board layout reference. Locate all bypass capacitors as close to the device as possible, prefer- ably on the same side as the ADC, using surface-

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