MIC23450-AAAYML - Electronic component Microchip - Free user manual and instructions

USER MANUAL MIC23450-AAAYML Microchip

MIC23450 Evaluation Board

3MHz, PWM, 2A Triple Buck Regulator with HyperLight Load® and Power Good

General Description

This board allows the customer to evaluate the MIC23450, a fully-integrated, triple-output, 2A, 3MHz switching regulator that features HyperLight Load ^® mode and power good (PG) output indicators. The MIC23450 is highly efficient throughout the output current range, drawing just 23 A of quiescent current for each channel in operation. The tiny 5mm x 5mm MLF ^® package saves board space and requires few external components. The MIC23450 provides ± 2.5% output voltage accuracy and each channel responds typically in less than 10 s to a load transient with as low as 5mV output voltage ripple.

Requirements

This board needs a single 40W bench power source, adjustable from 2.7V to 5.5V. The loads can be either active (electronic load) or passive (resistor), and must be able to dissipate 20W. It is ideal, but not essential, to have an oscilloscope available to view the circuit waveforms. The simplest tests require two voltage meters to measure input and output voltage. Efficiency measurements for a single channel require two voltage meters and two ammeters to prevent errors caused by measurement inaccuracies.

Precautions

There is no reverse input protection on this board. Be careful when connecting the input source to make sure correct polarity is observed.

Getting Started

1. Connect an external supply to the V_IN (J1) terminal and GND (J3).

With the output of the power supply disabled, set its voltage to the desired input test voltage (2.7V ≤ V IN ≤ 5.5V). An ammeter may be placed between the input supply and the V IN (J1) terminal. Be sure to monitor the supply voltage at the V _IN (J1) terminal, as the ammeter and/or power lead resistance can reduce the voltage supplied to the device.

1. Connect a load to the V_OUT terminals (J2, J5, J7) and ground (J4, J6, J8) terminals.

The load can be either active passive (resistive) or active (electronic load). An ammeter may be placed between the loads and the output terminals. Make sure the output voltage is monitored at V_OUT1 , V_OUT2 and V_OUT3 (J2, J5 and J7) terminals. The board has multiple 2-pin connectors (JP1, JP2 and JP3) to allow for output voltage monitoring of V_OUT1 , V_OUT2 and V_OUT3 respectively.

1. Enable the Supply to MIC23450.

The MIC23450 evaluation board has a pull-up resistor to V_IN for each channel. By default, each output voltage is enabled when the input supply of >2.7V is applied. Each channel 1, 2 or 3 can be disabled by applying a voltage below 0.4V to the EN terminal J10, J12 or J14 respectively.

1. Power Good.

The board provides a power good test point (J9, J11, and J13) to monitor the power good function for each of the channels 1, 2, and 3 respectively. The power good output goes high ( V_OUT ) nominally 62 s after the output voltage reaches 90% of its nominal voltage.

Ordering Information

Part Number Description
MIC23450-AAAYML EV	3MHz, PWM, 2A Triple Buck Regulator Evaluation Board

HyperLight Load is a registered trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademark Amkor Technology Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax [phone] • http://www.micrel.com

Evaluation Board

EN3 EN2 EN1 PG1 VOUT1 GND1 J4 J2 J6 J2 L1 J4 VOUT2 VIN T1 VIN1 C4 VING3 GND J3 VINC1 J1 J7 J5 GND2 MG3 MIC23450 YML PG3 GNDS VOUT3

Other Features

Soft-Start

The MIC23450 has an internal soft start for each individual channel and requires no external soft start capacitor. The typical soft-start time for each channel is 115μs.

Feedback Resistors (R4-R7, R12, R14)

The feedback pins FB1, FB2, and FB3 are the control inputs for programming the output voltages V_OUT1 , V_OUT2 and V_OUT3 respectively. Resistor divider networks are connected to these pins from the output and are compared to the internal 0.62V reference within the regulation loop. The output voltage can be programmed between 1V and 3.3V using resistor values calculated by Equation 1:

$$ \begin{array}{l} V = V _ {R E F O U} \left(1 + \frac {R 4}{R 5}\right) \ V = V _ {R E F O U T} \left(1 _ {2 ^ {+}} \frac {R 6}{R 7}\right) \quad E q. 1 \ V = V _ {R E F O U T 3} + \frac {R 1 2}{R 1 4} \ \end{array} $$

Example feedback resistor values are provided in Table 1.

Table 1 Output Voltage Programming Examples

VOUT1, VOUT2, VOUT3	R4, R6, R12	R5, R7, R14
1.2V	274k	294k
1.5V	316k	221k
1.8V	301k	158k
2.5V	324k	107k
3.3V	309k	71.5k

Power Good (PG1, PG2, PG3)

The evaluation board has test points for channels 1, 2, and 3 to monitor the PG1, PG2 and PG3 signals. These are open-drain connections to the corresponding output voltage with on-board pull-up resistors of 100kΩ. The PG signal will be asserted high approximately 62μs after the output voltage passes 90% of the nominal set voltage.

Hyper Light Load Mode

The MIC23450 uses a minimum on and off time proprietary control loop (patented by Micrel). When the output voltage falls below the regulation threshold, the error comparator begins a switching cycle that turns the PMOS on and keeps it on for the duration of the minimum-on-time. This increases the output voltage. If the output voltage is over the regulation threshold, the error comparator turns the PMOS off for a minimum-off-time until the output drops below the threshold. The NMOS acts as an ideal rectifier that conducts when the PMOS is off. Using an NMOS switch instead of a diode allows for lower voltage drop across the switching device when it is on. The asynchronous switching combination between the PMOS and the NMOS allows the control loop to work in discontinuous mode for light load operations. In discontinuous mode, the MIC23450 works in pulse frequency modulation (PFM) to regulate the output. As the output current increases, the off-time decreases, which provides more energy to the output. This switching scheme improves the efficiency of MIC23450 during light load currents by switching only when it is needed. As the load current increases, the MIC23450 goes into continuous conduction mode (CCM) and switches at a frequency centered at 3MHz. The equation to calculate the load when the MIC23450 goes into continuous conduction mode is approximated by Equation 2:

$$ I _ {\text {LOAD}} > \left(\frac {(V _ {\text {IN}} - V _ {\text {OUT}}) \times D}{2 L \times f}\right) \tag {Eq.2} $$

Equation 1 shows that the load at which MIC23450 transitions from HyperLight Load mode to PWM mode is a function of the input voltage ( V_IN ), output voltage ( V_OUT ), duty cycle (D), inductance (L), and frequency (f). The “Switching Frequency vs. Load” graph on page 3 shows that, as the output current increases, the switching frequency also increases until the MIC23450 goes from HyperLight Load mode to PWM mode at approximately 150mA. The MIC23450 will switch at a relatively constant frequency around 3MHz after the output current is over 150mA.

Multiple Sources

The MIC23450 provides all the pins necessary to operate the three regulators from independent sources. This can be useful in partitioning power within a multi rail system. For example, it is possible that within a system, two supplies are available; 3.3V and 5V. The MIC23450 can be connected to use the 3.3V supply to provide two, low voltage outputs (e.g. 1.2V and 1.8V) and use the 5V rail to provide a higher output (e.g. 2.5V), resulting in the power blocks shown in Figure 1.

5V 3.3V CH1 CH2 CH3 2.5V 1.8V 1.2V

Figure 1. Multi-Source Power Block Diagram

To achieve this multiple source configuration on the MIC23450YML EV, the PVIN and AVIN of each channel must first be isolated from the global VIN by removing the VIN resistor; R16 for Channel 1, R17 for Channel 2 and R18 for Channel 3. Once the global VIN is isolated, a separate VIN source may then be supplied to the isolated channel through the terminals provided (J15, J16 and J17) which are labeled VIN1, VIN2 or VIN3 according to which channel they supply.

Evaluation Board Performance

Efficiency vs. Output Current V_OUT = 2.5V

Efficiency vs. Output Current V_OUT = 1.8V

Line Regulation (Low Loads)

Line Regulation (High Loads)

Maximum Output Current per O/P vs. Temperature (1 O/P)

Maximum Output Current O/P vs. Temperature (2 O/Ps)

Maximum Output Current per O/P vs. Temperature (3 O/Ps)

Power Dissipation vs. Load Current (per Channel)

Maximum Package Dissipation vs. Ambient Temperature

MIC23450YML Evaluation Board Schematic

J1 VIN0 R18 0 R17 0 R16 0 VIN1 J15 VIN2 J16 VIN3 J17 GND J3 C4 220µF/6.3V PGND PGND3 PGND1 V1b V2b V3b R1 51 V1 R2 51 V2 R3 51 V3 C3 0.1µF C2 0.1µF C1 0.1µF SGND1 SGND2 SGND3 V1b V1 V2b V3b VOUT3 VOUT2 VOUT1 VOUT1 VOUT3 PGND1 29 AGND1 29 PVIN1 29 AVIN1 29 SGND2 7 AGND2 7 PVIN3 7 AVIN3 7 SGND3 11 AGND3 11 VOUT3 IC1 MIC23450-AAAYML SW1 26 PVIN1 27 AVIN1 28 SGND1 29 AGND1 29 PVIN2 29 AVIN2 29 SGND2 7 AGND2 7 PVIN3 7 AVIN3 7 SGND3 11 AGND3 11 VOUT3 L1 1µH/3A VOUT1 J2 VOUT1 C5 4.7µF/6.3V R4 301k JP1 C11 0.1µF R5 158k J4 GND1 PGND1 SGND1 VOUT2 R19 1k J5 VOUT2 L2 1µH/3A C9 4.7µF/6.3V R6 316k JP2 C12 0.1µF R7 221k J6 GND2 PGND2 SGND2 VOUT3 J7 VOUT3 L3 1µH/3A C10 4.7µF/6.3V R12 274k JP3 C13 0.1µF R14 294k J8 GND3 SGND3

Bill of Materials

Item	Part Number	Manufacturer	Description	Qty.
C1, C2,C3, C11, C12, C13	C1608X5R1E104K	TDK^(1)	Ceramic Capacitor, 0.1μF, 6.3V, X5R, Size 0603 6
	GRM188R60J104KD Murata	(2)
C4	EEUFR1A221	Panasonic^(3)	Electrolytic Capacitor, 220μF, 10V, Size 6.3mm	1
C5-C10	C1608X5R0J475K	TDK	Ceramic Capacitor, 4.7μF, 6.3V, X5R, Size 0603 6
	GRM188R60J475KE19D	Murata
R1, R2, R3	CRCW040251R0FKEA	Vishay^(4)	Resistor, 51Ω, Size 0402	3
R4	CRCW04023013FKEA	Vishay	Resistor, 301kΩ, Size 0402	1
R5	CRCW04021583FKEA	Vishay	Resistor, 158kΩ, Size 0402	1
R6	CRCW04023163FKEA	Vishay	Resistor, 316kΩ, Size 0402	1
R7	CRCW04022213FKEA	Vishay	Resistor, 221kΩ, Size 0402	1
R12	CRCW04022743FKEA	Vishay	Resistor, 274kΩ, Size 0402	1
R14	CRCW04022943FKEA	Vishay	Resistor, 294kΩ, Size 0402	1
R8, R9, R10, R11, R13, R15	CRCW04021003FKEA	Vishay	Resistor, 100kΩ, Size 0402	6
R16, R17, R18	CRCW08050000FKEA	Vishay	Resistor, 0Ω, Size 0805	3
L1, L2, L3	VLS3012ST-1R0N1R9	TDK	1μH, 2A, 60mΩ, L3.0mm x W3.0mm x H1.0mm	3
	LQH44PN1R0NJ0	Murata	1μH, 2.8A, 50mΩ, L4.0mm x W4.0mm x H1.2mm
U1	MIC23450-AAAYML	Micrel, Inc.(5)	3MHz PWM 2A Buck Regulator with HyperLight Load	1

Notes:
1. TDK: www.tdk.com.
2. Murata: www.murata.com.
3. Panasonic: www.panasonic.com.
4. Vishay: www.vishay.com.
5. Micrel, Inc.: www.micrel.com.

PCB Layout Recommendations

2203 (mil) 1482.871 (mil) PG3 MIC23450 YML VOUT1 GND1 VOUT2 J14 J12 J10 J9 J15 VIN1 R1B J16 VIN2 R17 R18 VIN3 J17 GND C4 J3 J13 J6 J5 J4 JP1 C5 G9 JP2 C10 L3 J11 R18 PG2 J6 J7 VOUT3 GNDS

Top Layer

2203 (mil) 1482.871 (mil)

Layer 2

PCB Layout Recommendations (Continued)

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