MIC22950YML Evaluation Board User Guide

MIC22950YML Evaluation Board
Integrated 10A Synchronous Buck
Regulator
General Description
The Micrel MIC22950 is a high-efficiency, 10A integrated
synchronous buck (step-down) regulator. The MIC22950 is
optimized for highest power density and achieves over
90% efficiency while switching at 400kHz to 2MHz. The
MIC22950 features integrated 10A MOSFETs, flexible
sequencing and tracking abilities.
This board enables the evaluation of the MIC22950. The
board is optimized for ease of testing, with all the
components on a single side. The voltage mode feedback
loop is designed to allow high bandwidth with just 2
external compensation components. The high-side
MOSFET is a P-Channel, allowing duty-cycle control up to
100%. The ultra high-speed control loop keeps the output
voltage within regulation even under extreme transient
load swings commonly found in FPGAs and low voltage
ASICs. The output voltage can be adjusted down to 0.7V
to address all low voltage power needs. The MIC22950
offers a full-range of sequencing and tracking options. The
EN/DLY pin combined with the PG/POR pin allows
multiple outputs to be sequenced in any way on turn-on
and turn-off using EN/DLY pin. The RC (Ramp Control™)
pin allows the device to be connected to another
MIC22950 device to keep the output voltages within a
certain delta V on start up.
Requirements
This board needs a single bench power source adjustable
over the input voltage of 2.6V< VIN < 5.5V that can provide
at least 10A of current. The load can either be active
(electronic load) or passive (resistor) with the ability to
dissipate the maximum load power while keeping
accessible surfaces ideally < 70°C.
Precautions
There is no reverse input voltage protection on this board.
When connecting an input source, ensure that correct
polarity is observed.
Under extreme load conditions such as short circuit
testing, input transients can be quite large if long test leads
are used. In such cases, a 1200µF, 10V Electrolytic
capacitor is installed at the VIN terminals to prevent over
voltage damage to the IC.
Getting Started
1. Connect VIN supply to the input terminals PVIN
and PGND. With the output of this supply
disabled, set its voltage to the desired input test
voltage (2.6V< VIN < 5.5V). This supply voltage
should be monitored at the test boards input
terminals to allow voltage drops in the test cables
(and ammeter if used) to be accounted for. An
ammeter can be added inline with the +VIN input
terminal to accurately measure input current.
2. Connect the loads to the output terminals
between VOUT and PGND. Again, this output
voltage should be monitored by connecting the
voltmeter at the VOUT and SGND terminals. An
ammeter can be added inline with the VOUT
terminal of the evaluation board to accurately
measure the output current.
Output voltage is set to 1.8V. Output voltage can
be changed by selecting the resistor R2.
The resistor divider network for a desired VOUT is
given by:
R2 =
R1
⎞
⎛ VOUT
⎜⎜
− 1⎟⎟
⎠
⎝ VREF
where VREF is 0.7V and VOUT is the desired output
voltage.
Initially, set the output load to 0A to check that the
output is regulating properly prior to loaded tests.
3. Enable the input supply. By default, the output
voltage is enabled when an input supply of > 2.6V
is applied. When this input threshold is crossed,
the enable pin capacitor (1nF) begins to charge at
1V/µs until it reaches 1.25V, where switching
begins. To test the Enable functions of the
MIC22950, a test point is provided.
Ordering Information
Part Number
Description
MIC22950YML EV
Evaluation Board with the Integrated
10A MIC22950 Device
Ramp Control is a trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
December 2009
M9999-122209-A
Micrel, Inc.
MIC22950 Evaluation Board
Other Features
DELAY Time Input
Adding an external capacitor to this DELAY pin allows the
Power Good delay to be adjusted to perform as a PowerOn Reset (POR). As with the RC pin, this pin has an
internal 1µA current source and sink. After EN pin voltage
is driven high, VOUT will start to rise (rate determined by RC
pin capacitor). As the FB pin voltage goes above 90% of
its nominal set voltage, DELAY pin voltage begins to rise
as the 1µA source charges the external capacitor. When
the threshold of 1.24V is crossed, POR/PG pin is asserted
high and DELAY pin continues to charge to a voltage SVIN.
When FB pin voltage falls below 90% of nominal, POR/PG
is asserted low immediately. However, if EN pin is driven
low, POR/PG pin voltage will fall immediately to the low
state and DELAY pin voltage will begin to fall as the
external capacitor is discharged by the 1µA current sink.
When the threshold of ((VTP+1.24V)-1.24V) is crossed (VTP
is the internal voltage clamp, VTP-=0.9V), VOUT will begin to
fall at a rate determined by the RC pin capacitor. As the
voltage change in both cases is 1.24V, both rising and
falling delays are matched.
EN/DLY Input
C13 creates a delay set by an internal 1µA source
charging to a 1.25V threshold. A switch (Q1) is used from
EN pin to ground as shutdown ‘SHDN’ control. The part
will exhibit approximately 1.3µs enable delay from ‘SHDN’
going low to the start of switching. Using a pulse generator
with a low impedance output connected to the EN/DLY
terminal will remove this delay as it defeats the internal
1µA source.
RC (Ramp Control™) Pin Capacitor
The MIC22950 has a nominal 1µA current source/sink to
the RC pin. The startup output voltage waveform tracks
the voltage on RC pin. 100% output voltage is represented
by 0.7V on RC pin. The default capacitor C12, 220pF on
RC pin sets the ramp up time to approximately 150µs.
Feedback Resistors
The output is set nominally at 1.8V. This can be changed
by adjusting the upper or lower resistor in the FB potential
dividers. It is recommended that R1 or R2 value should be
kept <10k to reduce noise susceptibility and offset currents
from creating voltage errors. Therefore, choosing R1<10k:
R2 = R1xVREF/(VO – VREF)
where VREF = 0.7V.
December 2009
POR (Power-On Reset) Output
This is an open drain connection with an on board pull-up
resistor (R4) to PVIN. This is only asserted high when the
FB pin reaches >90% of its nominal set voltage. This can
be used as part of the Tracking and sequencing function
described in the data sheet.
2
M9999-122209-A
Micrel, Inc.
MIC22950YML Evaluation Board
Evaluation Board Performances
100
Efficiency vs. Load Current
(VOUT=1.8V)
100
95
95
90
VIN = 3.6V
EFFICIENCY (%)
EFFICIENCY (%)
90
85
VIN = 2.6V
80
75
VIN = 5V
70
85
80
75
70
65
65
60
60
0
December 2009
Efficiency vs. Load Current
(VOUT=3.3V)
2
4
6
8
LOAD CURRENT (A)
0
10
2
4
6
8
10
LOAD CURRENT (A)
3
M9999-122209-A
Micrel, Inc.
MIC22950YML Evaluation Board
Evaluation Board Schematic
Bill of Materials
Item
C1, C2,
C3, C4
C5
Part Number
GRM21BR60J226ME39L
C2012X5R0J226K
C8
December 2009
TDK(2)
AVX(3)
GRM188R60J106ME47D
muRata
C1608X5R0J106K
VJ0603Y390KXXMB
C7
muRata(1)
08056D226MAT2A
06036D106MAT2A
C6
Manufacturer
TDK
AVX
Vitramon(4)
06033A390FAT2A
AVX
C1608C0G1H390J
TDK
VJ0603Y101KXAAT
Vitramon
06025A101KAT2A
AVX
C1608C0G1H101J
TDK
VJ0603Y391KXAAT
Vitramon
06035A391JAT2A
AVX
C1608C0G1H391J
TDK
4
Description
Qty.
Ceramic Capacitor, 22µF, 6.3V, X5R,
0805
4
Ceramic Capacitor, 10µF, 6.3V, X5R,
0603
1
Ceramic Capacitor, 39pF, 25V, X7R,
0603
1
Ceramic Capacitor, 100pF, 50V,
0603
1
Ceramic Capacitor, 390pF, 50V,
0603
1
M9999-122209-A
Micrel, Inc.
MIC22950YML Evaluation Board
Bill of Materials (continued)
Item
Part Number
GRM31CR60J476ME19L
C9. C10
Manufacturer
muRata
C3216X5R0J476M
TDK
12066D476MAT2A
AVX
Description
Qty.
Ceramic Capacitor, 47µF, 6.3V,
1206
2
C11
C13
VJ0603Y102KXXMB
Vitramon
Ceramic Capacitor, 1nf, 50V, 0603
1
C14
VJ0603Y103KXXMB
Vitramon
Ceramic Capacitor, 10nf, 50V, 0603
1
C12
06035A121JAT2A
AVX
C1608COG1H121J
TDK
GRM1885C1H121JA01D
muRata
CIN
EEE-FPA122UAP
L1
CDEP105ME-1R2MC
Sumida(5)
1
1.2µH, 21A , Inductor
1
R1
CRCW06031101FRT1
Vishay Dale(4)
Resistor, 1.1k, 1%, 0603
1
R2
CRCW0603698RFRT1
Vishay Dale
Resistor, 698Ω, 1%, 0603
1
R3
CRCW06032002FRT1
Vishay Dale
Resistor, 20k, 1%, 0603
1
R4
CRCW06034752FRT1
Vishay Dale
Resistor, 47.5k 1%, 0603
1
R5
CRCW06031003FRT1
Vishay Dale
Resistor, 100k 1%, 0603
1
U1
2N7002E(SOT-23)
Panasonic(7)
Electrolitic
1200uF, 10V, 10x10.2-Case
Q1
Notes:
1.
Ceramic Capacitor, 120pF, 50V,
COG, 0603
Vishay Corp
CMDPM7002A
Central Semiconductor(5)
MIC22950YML
Micrel(6)
1
Signal MOSFET-SOT-236
10A Integrated Switch
Synchronous Buck Regulator with
Frequency Programmable to 2MHz
1
TDK: www.tdk.com
2.
AVX: www.avx.com
3.
muRata: www.murata.com
4.
Vishay: www.vishay.com
5.
Central Semiconductor: www.centralsemi.com
6.
Micrel, Inc.: www.micrel.com
7.
Panasonic: www.panasonic.com
December 2009
5
M9999-122209-A
Micrel, Inc.
MIC22950YML Evaluation Board
PCB Layout Recommendations
Top Layer
Bottom Layer
December 2009
6
M9999-122209-A
Micrel, Inc.
MIC22950YML Evaluation Board
PCB Layout Recommendations (continued)
Middle Layer
Middle Layer
December 2009
7
M9999-122209-A
Micrel, Inc.
MIC22950YML Evaluation Board
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2008 Micrel, Incorporated.
December 2009
8
M9999-122209-A