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Microchip Inte kategoriserad MIC23450-AAAYML

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Sida 1/9

MIC23450 Evaluation Board

3 , , MHz PWM 2A Triple Buck Regulator

with HyperLight Load

and Power Good

HyperLight Load is a trademark of Micrel, Inc.registered

MLF and LeadFrame are registered trademark Amkor Technology Inc.Micro

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 ( ) 944 0800 • fax + 1 (408) 474 1000 • 408 - - http://www.micrel.com

February 4, 2013

Revision 1.0

General Description

This board allows the customer to evaluate the

MIC23 output 3MHz450, a fully integrated, triple- - , 2A,

switching regulator that features HyperLight Load ® mode

and ood 450 power g (PG) output indicator . The MIC23s

is highly efficient throughout the output current range,

drawing just 23 A of quiescent cu for each channel µ rrent

in operation. The tiny 5mm x 5mm MLF® package saves

board space and requires few external components. The

MIC23450 provides 2.5% accuracy and± output voltage

each channel typically in less than 10 to a responds µs

load transient with output voltage ripple.as low as 5mV

Requirements

This board needs a single 40W bench power source,

adjustable from to 5.5 . The loads can 2.7V V be either

active (electronic load) or passive (re and must be sistor),

able to to dissipate 20W. It is ideal, but not essential,

have an oscilloscope available to view the circuit

waveforms. require oltage The simplest tests vtwo

meters to measure input and output voltage. Efficiency

measurements require oltage for a single channel vtwo

meters and meterstwo am to prevent errors caused by

measurement inaccuracies.

Precautions

There is no reverse input protection on this board. Be

careful make when connecting the input source to sure

correct polarity is observed.

Getting Started

1. Connect an external supply to the VIN ) (J1

terminal and (JGND 3).

With the output of the power supply disabled, set its

voltage to the desired input test voltage (2.7V ≤ VIN ≤

5.5V). An ammeter may be placed between the input

supply and the VIN ( ) . J1 terminal Be sure to monitor

the supply voltage at the VIN ( ) J1 terminal, as the

ammeter and/or power lead resistance can reduce

the voltage supplied to the device.

2. Connect a load Vto the 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 load and the output terminals s. Make

sure the output voltage is monitored at VOUT1, VOUT2

and VOUT3 ( ) s. J2, J5 and J7 terminal The board has

multiple 2- s ) pin connector (JP1, JP2 and JP3 to

allow for output voltage monitoring of VOUT1

, VOUT2

and VOUT3 . respectively

3. Enable the Supply to MIC23450.

The MIC23450 evaluation up board has a pull-

resistor to VIN for each channel By default, . each

output voltage bled when the input supply of is ena

> V 2.7 is applied. Each channel 1, 2 or 3 can be

disabled by the Eapplying 0.4 a voltage below V to N

terminal or J14 respectivelyJ10, J12 .

4. Power Good.

The board provides a test point power ood g (J9,

J11, and J13 to monitor for ) the power good function

each channel The of the s 1, 2, and 3 respectively.

power good output high (goes VOUT) nominally 62 µs

after reaches the output voltage 90% of its nominal

voltage.

Ordering Information

Part Number Description

MIC23 YML450-AAA EV 3MHz, PWM,

2A Triple Buck

R egulator Evaluation Board

Micrel, Inc.

MIC23450 Evaluation Board

February 4, 2013 2 Revision 1.0

Evaluation Board

Other Features

S -S oft tart

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 , R14 -(R4 R7, R12 )

The feedback pin the control s , FB1, FB2 and are FB3

inputs for programming the output voltages VOUT1, VOUT2

and VOUT3 R s respectively. esistor divider network are

connected to from the output and these pin s 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:











+⋅=











+⋅=











+⋅=

R14

R12

1VV

REFOUT3

REFOUT2

REFOUT1

Eq. 1

Example feedback resistor values are provided in Table

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 as test point s 1, 2, h s for channel

and 3 to monitor the PG 1, PG2 and PG3 signal These s.

are open to the corresponding output -drain connections

voltage of with on-board pull up resistor- s 100kΩ. The

PG signal will be µs asserted high approximately 62 after

the output voltage passes nominal set 90% of the

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 a NMOS switch instead of a diode n

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 . The 3MHz

equation to calculate the load when the MIC23450 goes

into continuous conduction mode is approximated by

Equation 2:













×−

>f2L

D)V(V

OUTIN

LOAD

2 Eq.

Micrel, Inc.

MIC23450 Evaluation Board

February 4, 2013 3 Revision 1.0

Equation 1 shows that the load at which MIC23 450

transitions from HyperLight Load mode to PWM mode is

a function of the input voltage (VIN), output voltage

(VOUT), duty cycle (D), inductance (L) and frequency (, f).

T “ . ” he Switching Frequency vs Load graph on page 3

shows that, as the urrent increases, the output c

switching frequency also increases until the MIC23450

goes from HyperLight Load mode to PWM mode at

approximately 450150mA. The MIC23 will switch at a

relatively constant frequency around 3MHz after the

output current is over 150 mA.

Multiple Sources

The MIC23450 provides all the pins necessary to

operate the regulators from independent sources. three

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.

Figure 1. Multi- Source Power Block Diagram

To achieve this multiple source configuration on the

MIC23450YML EV, the PVIN of each channel and AVIN

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.

Produktspecifikationer

Varumärke:	Microchip
Kategori:	Inte kategoriserad
Modell:	MIC23450-AAAYML

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