MIC39100/39101/39102 Evaluation Board

MIC39100/39101/39102
Micrel
MIC39100/39101/39102 Evaluation Board
1A Low-Voltage Low-Dropout Regulator
that indicates when the output falls out of regulation for any
reason. The error flag output is an open-collector output,
which is active-low, and requires a pull-up resistor for proper
operation. Boards assembled with the MIC39101 have a
47kΩ pull-up resistor from FLG to the input voltage.
The MIC39102 is an adjustable regulator that implements an
enable pin that allows the user to disable the device. The
enable pin is also active-high and requires that pin to be
pulled high to turn-on the output and pulled low to disable the
output. A jumper (JP1)is available to tie that pin to either the
input or to ground. The output voltage of the MIC39102 is
adjustable down to the band gap voltage of 1.24V. The board
is set up with four set voltage options, A through D. A fifth
option is available that can be custom set. The equation to set
the output voltage is as follows:
General Description
This evaluation board can be used to evaluate several of
Micrel’s new, low voltage, high current, low-dropout linear
voltage regulators. The MIC39100 is a three-terminal LDO
offered in the SOT-223 surface mount, power package. The
MIC39101 is a 1A LDO in a power SO-8 package that offers
the added functionality of an enable pin and an error flag
output. The MIC39102 is an adjustable version of the
MIC39100 in a power SO-8 package and it also has the added
functionality of an enable pin, allowing the user to disable the
device and put it into a zero-current off mode state. The board
has two layouts, one on the topside to accommodate the
MIC39100 and one on the backside to accommodate the
MIC39101/2. This one board can easily be used to evaluate
any one of these parts.
 R1
VOUT = VREF 1 +

 R2 
Requirements
The evaluation board requires a power supply capable of
supplying a minimum of 1A of output current. The maximum
voltage of that power supply should be at least 5V. These
parts are intended for 3.3V to 2.5V and 3.3V or 2.5V to 1.8V
conversion. A high voltage power supply should not be
needed. The MIC39100/1/2 has an input voltage range of
2.25V to 16V, therefore it is not limited to just 5V systems.
VREF = 1.24V
On the board as it stands, R1 is set to 10kΩ. Using the
equation and knowing that R1 = 10kΩ, a custom voltage can
be determined by solving for R2 and placing an 0805 or 1206
resistor in the slot prepared and labeled E.
Circuit Description


VREF
R2 = 
 × R1
−
V
V
 OUT
REF 
The MIC39100/1/2 regulators are simple to implement, requiring only an output capacitor for proper operation. An input
cap is required when the power supply is greater than 4” away
from the device. All evaluation boards include an input
capacitor within 1” of the device. This is the recommended
maximum distance away from the device that a capacitor
should be placed.
A minimum of 10µF of output capacitance is required for the
MIC39100/1/2. Using large values of capacitance at the input
and output will help to improve transient response. Table 1
shows the bill of materials for the different devices.


1.24V
R2 = 
 × 10kΩ
 VOUT − 1.24V 
Leaving all jumpers open sets the output voltage to the band
gap voltage, 1.24V.
Minimum Load
All of the devices require a minimum load of 10mA. A resistor
is included on the board to provide a minimum load of 10mA.
The resistor value is different depending on the voltage option
that the board has. The MIC39102 has a 140Ω resistor to
maintain approximately 10mA at 1.4V output voltage. The
140Ω resistor can be changed to set a 10mA load depending
upon the desired output voltage.
MIC39101/MIC39102
The MIC39101 circuit implements an error flag and an enable
function. The enable function allows the user to put the device
into a zero-current off state when the regulator is not required.
The enable pin is an active-high pin and needs to be pulled
high (>2V) to enable the device and pulled low (< 0.8V) to
disable the device. The error flag function is a voltage monitor
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
August 2000
1
MIC39100/39101/39102
MIC39100/39101/39102
Micrel
MIC39100-x.xBM
VIN
IN
VOUT
OUT
C2B
C1B
R1B
GND
GND
Figure 1. MIC39100, SOT-223 Regulator Schematic
MIC39101-X.XBM
IN
OUT
VIN
J2
C1
VOUT
J5
R8
C2
R7
1
JP1
1–2 = on
2–3 = off
Floating = off
EN
2
3
GND
FLG
J3 FLAG
J4
GND
J6
Figure 2. MIC39101, Power SOP-8 Regulator Schematic
MIC39102BM
IN
OUT
VIN
J2
VOUT
J5
C1
C2
R6
10kΩ
R8
R5
R4
R3
R2
R1
76.8kΩ
47.5kΩ
30.1kΩ
22.1kΩ
open/custom
1
1–2 = on
2–3 = off
Floating = off
JP1
EN
2
3
GND
ADJ
J3
J4
GND
J6
GND
Figure 3. MIC39102, Adjustable Regulator Schematic
MIC39100/39101/39102
2
August 2000
MIC39100/39101/39102
Micrel
Bill of Materials
Item
Part Number
C1B
TPSC106M025R0500
AVX
10µF, 25V, Tantalum
C2B
TPSC106M025R10500
AVX
10µF, 25V, Tantalum
1
AVX
240Ω (2.5V) or 180Ω (1.8V) 5% 1/8W
1
LDO Regulator
1
R1B
Manufacturer
Description
Micrel
Qty.
1
U1B
MIC39100-x.xBS
C1
TPSC106M025R0500
AVX
10µF, 25V, Tantalum
1
C2
TPSC106M025R10500
AVX
10µF, 25V, Tantalum
1
470Ω 5% 1/8W, size 0805
1
R7
R8
AVX
240Ω (2.5V) or 180Ω (1.8V) 5% 1/8W
1
LDO Regulator
1
AVX
10µF, 25V, Tantalum
1
AVX
10µF, 25V, Tantalum
1
R2
22.1k 1% 1/8W, size 0805
1
R3
30.1k 1% 1/8W, size 0805
1
R4
47.5k 1% 1/8W, size 0805
1
R5
76.8k 1% 1/8W, size 0805
1
R6
10k 1% 1/8W, size 0805
1
140Ω 1% 1/8W, size 0805
1
LDO Regulator
1
U1
MIC39101-x.xBM
C1
TPSC106M025R0500
C2
TPSC106M025R0500
R1
Open
R7
Micrel
Open
R8
U1
August 2000
MIC39102BM
Micrel
3
MIC39100/39101/39102
MIC39100/39101/39102
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2000 Micrel Incorporated
MIC39100/39101/39102
4
August 2000