MIC2205YML Evaluation Board User Guide

MIC2205 Evaluation Board
High Efficiency 2Mhz Step-Down
Converter with LOW™ Mode
General Description
The Micrel MIC2205 is a high efficiency 2MHz PWM
synchronous step-down switching regulator that
features a LOWQ™ LDO standby mode that draws
only 18µA of quiescent current. The MIC2205
features an ultra-low noise, small size, and high
efficiency solution for portable power applications.
In PWM mode, the MIC2205 operates at a constant
frequency of 2MHz. Under light load conditions, such
as in system sleep or standby modes, the PWM
switching operation can be disabled to reduce
switching losses. In this light load LOWQ™ mode, the
LDO maintains the output voltage and draws only
18µA of quiescent current. The LDO mode of
operation saves battery life while not introducing
spurious noise and high ripple as experienced with
pulse skipping or bursting mode regulators.
The MIC2205 operates from a 2.7V to 5.5V input and
features internal power MOSFETs that can supply up
to 600mA of output current in PWM mode. It can
operate with a maximum duty cycle of 100% for use
in low-dropout conditions.
Requirements
The MIC2205 evaluation board requires an input
power source that is able to deliver greater than 1A at
2.7V. The output load can either be an active or
passive source.
Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the VIN
terminal may damage the device.
In addition, the maximum operating voltage of the
MIC2205 evaluation board is 5.5V. Exceeding 6V on
the input could damage the device.
Getting Started
1. Connect an external supply to VIN
terminal. Apply desired input voltage to the
VIN and ground terminals of the evaluation
board, paying careful attention to polarity
and supply voltage (2.7V ≤ VIN ≤ 5.5V). An
ammeter may be placed between the input
supply and the VIN terminal to the evaluation
board. Be sure to monitor the supply voltage
at the VIN terminal. The ammeter and/or
power lead resistance can reduce the
voltage supplied to the input.
2. Connect the load to the VOUT and ground
terminals. The load can be either passive
(resistive) or active (electronic load). An
ammeter can be placed between the load
and the VOUT terminal. Ensure the output
voltage is monitored at the VOUT terminal.
The default output voltage is set to 1.8V.
This can be adjusted by changing the
feedback resistors. (see Output Voltage).
3. Enable the MIC2205. Apply a 1.3V or
greater voltage source to the enable pin.
LOWQ 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
M9999-051606
May 2006
(408) 955-1690
Micrel, Inc
MIC2205 Evaluation Board
LOWQTM
The MIC2205 is a 600mA PWM power device that
utilizes a LOWQ™ light load mode to maximize
battery efficiency in light load conditions. This is
achieved with a LOWQ™ control pin that when pulled
low, (Remove JP1), shuts down all the biasing and
drive current for the PWM regulator, drawing only
18µA of operating current. This allows the output to
be regulated through the LDO output that is capable
of providing 60mA of output current. This method has
the advantage of producing a clean, low current, ultra
low noise output in LOWQ™ mode. During LOWQ™
mode, the SW node becomes high impedance,
blocking current flow. Other methods of reducing
quiescent current, such as pulse frequency
modulation (PFM) or bursting techniques, create large
amplitude, low frequency ripple voltages that can be
detrimental to system operation.
Output Voltage
The output voltage on the MIC2205 evaluation board
is adjustable. The output voltage is controlled by the
feedback resistors (R1 and R2) and can be
calculated as follows:
⎛ R1 ⎞
+ 1⎟
VOUT = 1.0V × ⎜
⎝ R2
⎠
The evaluation board is initially adjusted to 1.8V, but
can easily be modified by removing R2 and
replacing it with the value that yields the desired
output voltage. (Removing R2 sets the output to
1.0V).
R2 =
May 2006
100kΩ
⎛ VOUT
⎞
⎜⎜
− 1⎟⎟
⎝ 1.0V
⎠
When more than 60mA is required, the LOWQ pin
can be forced high, (Connect JP1), causing the
MIC2205 to enter PWM mode. In this case, the LDO
output makes a "hand-off" to the PWM regulator
virtually without any variation in output voltage. The
LDO output then turns off allowing up to 600mA of
current to be efficiently supplied through the PWM
output to the load.
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M9999-051606
(408) 955-1690
Micrel, Inc.
MIC2205 Evaluation Board
VIN 2.7V to 5.5V
8
R3
10K
C2
0.1µF
4
6
C1
1µF
R4
10K
C3
0.1µF
GND
MIC2205BML/YML
VIN
SW
AVIN
LDO
EN
7
LOWQ
3
BIAS
AGND
1
9
VOUT 1.8V
L1
2.2µH
600mA
2
C5
2.2µF
R1
100K
FB
PGND
5
C4
120pF
R2
124K
10
GND
Bill of Material
MIC2205 Evaluation Board
Ref Des
Part Number
06036D475MAT2A
C1608X5R0J475M
C1005X5R1C104K
GRM155R61C104K
C1005X5R1C104K
GRM155R61C104K
VJ0402A121KXJAT
06036D225MAT2A
GRM188R60J225KE19D
C1608X5R1A225K
LQH32CN2R2M53
VLF3010AT-2R2M1R0
CBC2016T2R2M
CRCW04021003FRT1
CRCW04021243FRT1
CRCW04021002FRT1
CRCW04021002FRT1
MIC2205BML/YML*
C1
C2
C3
C4
C5
L1
R1
R2
R3
R4
U1
Description
Manufacturer
4.7µF 6.3V X5R 0603 Ceramic Capacitor
0.1µF 16V X5R 0402 Ceramic Capacitor
0.1µF 16V X7R 0402 Ceramic Capacitor
0.1µF 16V X5R 0402 Ceramic Capacitor
0.1µF 16V X7R 0402 Ceramic Capacitor
120pF 16V X7R 0402 Ceramic Capacitor
2.2µF 6.3V X5R 0603 Ceramic Capacitor
2.2µF 10V X5R 0603 Ceramic Capacitor
2.2µH 790mA Inductor
2.2µH 100mA Inductor
2.2µH 750mA Inductor
100kΩ 1% 0402 Resistor
124kΩ 1% 0402 Resistor
10kΩ 1% 0402 Resistor
10kΩ 1% 0402 Resistor
2MHz PWM Step-Down Converter/LDO
TDK
Murata
TDK
Murata
TDK
Murata
Vishay
AVX
Murata
TDK
Murata
TDK
Taiyo Yuden
Vishay
Vishay
Vishay
Vishay
Micrel
Notes:
1.
AVX: www.avx.com
2.
Murata: www.murata.com
3.
TDK: www.tdk.com
4.
Vishay: www.vishay.com
5.
Taiyo Yuden: www.t-yuden.co
6.
Micrel, Inc.: www.micrel.com
* Micrel IC = Pb-Free
May 2006
3
M9999-051606
(408) 955-1690
Micrel, Inc.
MIC2205 Evaluation Board
Printed Circuit Board Layouts
May 2006
Figure 1a. Top Silkscreen
Figure 1b. Top Layer
Figure 1c. Bottom Silkscreen
Figure 1d. Bottom Layer
4
M9999-051606
(408) 955-1690
Micrel, Inc.
MIC2205 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
This 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.
© 2005 Micrel Incorporated
May 2006
5
M9999-051606
(408) 955-1690