Micrel MIC45208 User Manual

General Description

MIC45208 Evaluation Board

26V/10A DC-to-DC Power Module

Getting Started

Micrel’s MIC45208 is a synchronous step-down regulator
module, featuring a unique adaptive ON-time control
architecture. The module incorporates a DC-to-DC
controller, power MOSFETs, bootstrap diode, bootstrap
capacitor, and an inductor in a single package; sim plifying
the design and layout process for the end user.

This highly-integrated solution expedites system design
and improves product time-to-market. The internal
MOSFETs and inductor are optimized to achieve high
efficiency at a low output voltage. The fully optimized
design can deliver up to 10A current under a wide input
voltage range of 4.5 V to 26V, without requiring add itional
cooling.

®

The MIC45208-1 uses Micrel’s HyperLight Load

(HLL)
MIC45208-2 uses Micrel’s Hyper Speed Control™
architecture which enables ultra-fast load transient
response, allowing for a reduction of output capacitance.
The MIC45208 offers 1% output accuracy that can be
adjusted from 0.8V to 5.5V with two external resistors.

The basic parameters of the evaluation board are:

• Input: 4.5V to 26V

• Output: 0.8V to 5V at 10A

• 600kHz Switching Frequency

(Adjustable 200kHz to 600kHz)

Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com

.

Requirements

The MIC45208-1 and MIC45208-2 evaluation board only
requires a single power supply with at least 10A current
capability. No external linear r egulator is requ ired to p ower
the internal biasing of t he IC because the MIC45208 has
an internal PVDD LDO. In applications where VIN < +5.5V,
PVDD shoul d be tied to VIN to bypass the internal linear
regulator. The output load can either be a passive or an
active load.

1. VIN Supply

Connect a power supply to the VIN and GND
terminals, paying careful attention to the polarity and
the supply range (4.5V < V IN < 26V). Monitor IIN with
a current meter and monitor input vol tage at VIN and
GND terminals with a voltmeter. Do not apply power
until Step 4.

2. Connect Load and Monitor Output

Connect a load to the VOUT and GND terminals. The
load can be either a pas si v e (r es isti ve) or a n ac t ive ( a s
in an electronic load) type. A current meter may be
placed between the VOUT terminal and load to
monitor the output current. Ensure the output voltage
is monitored at the VOUT terminal.

3. Enable Input

The EN pin has an on-board 100kΩ pull-up resistor
(R10) to VIN, which allo ws the output to be turned o n
when PVDD exceeds its UVLO threshold. An EN
connector is provided on the evaluation board for
users to easily acc ess the enable feature. Ap plying an
external logic signal on the EN pin to pull it low or
using a jumper to short the EN pin to G ND will shut off
the output of the MIC45208 evaluation board .

4. Turn Power On

Turn on the VIN supply and verify that the output
voltage is regulated to 5V.

Ordering Information

Part Number Description

MIC45208-1YMP EV MIC45208-1 Evaluation Board
MIC45208-2YMP EV MIC45208-2 Evaluation Board

Precautions

The MIC45208 evaluation board does not have reverse
polarity protection. Applying a negative voltage to the VIN
and GND terminals can damage the de vice . The maximum
VIN of the board is rated at 30V. Exceeding 30V on the
VIN could damage the device.

HyperLight Load is a registered trademark and Hyper Speed Control is a trademark of Micrel, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com

August 19, 2015

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Micrel, Inc.

MIC45208 Evaluation Board

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













+×=

BOTTOM

REF

OUT

R

R14

1VV

REFOUT

REF

BOTTOM

VV

VR1

R

−

×

=

(Top Feedback Resistor)

(Bottom Feedback Resistor)

Features

Feedback Resistors

The output voltage on the MIC45208 evaluation board,
which is preset to 5.0V, is determined by the feedback

All other voltages not listed abo ve can b e set b y modifying
R

value according to:

BOTTOM

divider:

where V

REF

Leaving the R

= 0.8V, and R

open by removing all jum pers on the

BOTTOM

Eq. 1

is one of R3 thru R9.

BOTTOM

Eq. 2

Note that the output volt age should not be set to exceed
5V.

feedback headers gives a 0.8V output voltage.

Table 1. Typical Values of Some Components

V

VIN

OUT

1.0V 5V to 26V 10kΩ 40.2kΩ 2.2nF 100µF/6.3V

1.2V 5V to 26V 10kΩ 20kΩ 2.2nF 100µF/6.3V

R14

R

C12
(C

ff

C

)

OUT

1.5V 5V to 26V 10kΩ 11.5kΩ 2.2nF 100µF/6.3V

1.8V 5V to 26V 10kΩ 8.06kΩ 2.2nF 100µF/6.3V

2.5V 5V to 26V 10kΩ 4.75kΩ 2.2nF 100µF/6.3V

3.3V 5V to 26V 10kΩ 3.24kΩ 2.2nF 100µF/6.3V
5V 7V to 26V 10kΩ 1.9kΩ 2.2nF 100µF/6.3V

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MIC45208 Evaluation Board

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( )

CL

CL)ON(DS

PP

LCLIM

I

VR)5.0II(

R15

+××D−

=

L f V

)V(VV

I

swIN(MAX)

OUTIN(MAX)OUT

L(PP)

××

−×

=D

SW Node

Test point TP12 (V

) is placed for monitoring the

SW

switching waveform, which is one of the most critical
waveforms for the converter.

The short circuit curr ent lim it can be pro gramm ed by using
the following formula:

Current Limit

The MIC45208 uses the R

of the l ow-side MOSFET

DS(ON)

and external resistor connected from the ILIM pin to the
SW node to decide the current limit.

Figure 1. MIC45208 Current Limiting Circuit

During each switching c ycle of the MIC 45208, th e induc tor
current is sensed by monitoring the low-side MOSFET in
the OFF period. The sensed voltage, V

, is compared

(ILIM)

with the power ground (PGND) after a blanking time of
150ns. In this way the drop voltage over the resistor R15

) is compared with the drop over the bottom FET

(V

CL

generating the short current limit. The small capacitor
(C11) connected from ILIM pin to PGND filters the
switching node ringi ng duri ng the off-t ime allowing a better
short-limit measurement. The time constant created by
R15 and C11 should be muc h less than the minimum off
time.

The V

drop allows progr a m m ing of s hor t lim it thr oug h the

CL

value of the resistor (R15) if the absolute value of the
voltage drop on the bott om F ET is greater th an V
case the V

is lower than PGND and a short circuit

(ILIM)

. In that

CL

event is triggered. A hiccup c ycle to treat the s hort eve nt is
generated. The hiccup sequence including the soft start
reduces the stress on the switc hing FETs and protec ts the
load and supply for severe short conditions.

Eq. 3

I

= Desired current limit

CLIM

R

= On-resistance of low-side power MO SFET, 6mΩ

DS(ON)

(typ.)

= Current-limit threshold (typical absolute value is

V

CL

14mV per Electrical Characteristics table in MIC45208
datasheet)

= Current-limit source current (typical value is 70µA,

I

CL

per the Electrical Characteristics table in MIC45208
datasheet).

= I nductor current peak-to-peak, since the inductor

ΔI

L(PP)

is integrated use Equation 4 to calcu lat e t he in duc tor ripple
current.

The peak-to-peak inductor current ripple is:

Eq. 4

The MIC45208 has 0.8µH inductor integrated into the
module. In case of hard short, the short limit is folded
down to allow an indefinite hard short on the output without
any destructive effect. It is mandatory to make sure that
the inductor current use d to charge th e output c apacitance
during soft-start is under the folded short limit; otherwise
the supply will go in hiccup mode and m ay not be f inishing
the soft start successfully.

The MOSFET R
Therefore, it is recomm ended to add a 50% margin to I

DS(ON) varies 30 to 40% with temperature.

CLIM

in the above equation to avoid f alse current limiting du e to
increased MOSFET junction temperature r ise. With R15 =

1.37kΩ and C11 = 15pF, the t ypical output current lim it is

16.8A.

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MIC45208 Evaluation Board

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2R1R

2R

ff

OSW

+

×=

0

100

200

300

400

500

600

700

800

10.00 100.00 1000.00 10000.00

SW FREQ (kHz)

R2 (kΩ)

Switching Frequency

V

OUT

= 5V

V

= 12V

R1 = 100kΩ

Setting the Switching Frequency

The MIC45208 switching frequency can be adjusted by
changing the value of res istors R1 and R2. The switching

, V

frequency also depends on V

IN

, and load conditions.

OUT

R2 is selected to s et the required switching frequenc y as
shown in Figure 3:

Figure 2. Switching Frequency Adjustment

Equation 5 illustrates the estimated switching frequency:

Eq. 5

Where fO = 600kHz
R1 = 100kΩ (recommended)

Figure 3. Switching Frequency vs. R2

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C11

MIC45208 Evaluation Board Schematic

Bill of Materials

Item Part Number Manufacturer Description Qty.

C1 B41125A7227M000 TDK(1) 220µF/35V, ALE Capacitor (optional) 1
C2, C3 C3216X5R1H106M160AB TDK 10µF/50V, 1206, X5R, 10%, MLCC 2
C2X, C9, C10, C7,

C7X, C13
C4, C8, C14 GRM188R71H104KA93D Murata(2) 0.1µF/50V, X7R, 0603, 10%, MLCC 3
C5, C6 C3216X5R0J107M160AB TDK 100µF/6.3V, X5R, 1206, 20%, MLCC 2

C11 GRM1885C1H150JA01D Murata 15pF/50V, NP0, 0603, 5%, MLCC 3
C12 C1608C0G1H222JT TDK 2.2nF/50V, NP0, 0603, 5%, MLCC 1
CON1, CON2,

CON3, CON4

Notes:

1. TDK: www.TDK.com

2. Murata: www.murata.com.

3. Keystone: www.keyelco.com.

Open 6

(3)

8191k Keystone

.

15A, 4-Prong Through-Hole Screw Terminal 4

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Item

Part Number

Manufacturer

Description

Qty.

Bill of Materials (Continued)

J1 M50-3500742 Harwin(4) Header 2x7 1
J2, J3, J4, TP3 − TP5
R1, R10 CRCW0603100K0FKEA Vishay Dale(6) 100kΩ, 1%, 1/10W, 0603, Thick Film 2
R2, R12, R13, R16 Open 4
R3 CRCW060340K2FKEA Vishay Dale 40.2kΩ, 1%, 1/10W, 0603, Thick Film 1
R4 CRCW06020K0FKEA Vishay Dale 20kΩ, 1%, 1/10W, 0603, Thick Film 1
R5 CRCW060311K5FKEA Vishay Dale 11.5kΩ, 1%, 1/10W, 0603, Thick Film 1
R6 CRCW06038K06FKEA Vishay Dale 8.06kΩ, 1%, 1/10W, 0603, Thick Film 1
R7 CRCW06034K75FKEA Vishay Dale 4.75kΩ, 1%, 1/10W, 0603, Thick Film 1
R8 CRCW06033K24FKEA Vishay Dale 3.24kΩ, 1%, 1/10W, 0603, Thick Film 1
R9 CRCW06031K91FKEA Vishay Dale 1.91kΩ, 1%, 1/10W, 0603, Thick Film 1
R11 CRCW060349K9FKEA Vishay Dale 49.9kΩ, 1%, 1/10W, 0603, Thick Film 1
R14 CRCW060310K0FKEA Vishay Dale 10kΩ, 1%, 1/10W, 0603, Thick Film 1
R15 CRCW06031K37FKEA Vishay Dale 1.37kΩ, 1%, 1/10W, 0603, Thick Film 1
R17, R18, R19 RCG06030000Z0EA Vishay Dale 0Ω Resistor, 1%, 1/10W, 0603, Thick Film 3
TP7 − TP14

U1

Notes:

4. Harwin: www.harwin.com

5. Molex: www.molex.com.

6. Vishay-Dale: www.vishay.com.

7. Micrel: www.micrel.com.

90120-0122 Molex(5) Header 2 6

1502-2 Keystone Single-End, Through-Hole Terminal 8

MIC45208-1YMP
MIC45208-2YMP

.

Micrel, Inc.(7) 26V/10A DC-to-DC Power Module 1

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PCB Layout Recommendations

MIC45208 Evaluation Board Top Layer

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MIC45208 Evaluation Board Copper Layer 2

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MIC45208 Evaluation Board

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PCB Layout Recommendations (Continued)

MIC45208 Evaluation Board Copper Layer 3

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MIC45208 Evaluation Board Bottom Layer

Revision 2.0

Micrel, Inc.

MIC45208 Evaluation Board

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MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

Micrel, Inc. is a leading global m anufacturer of IC sol utions for the worldwide high

communications

markets. The Company’s products include advanced mixed

performance communication, clock

management,

Company
customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunications, automotive, and comp
Corporation headquarters and state

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information is not intended as a warranty and Micrel does not assume responsibility for its use.

t to change circuitry,
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