MIC23250-GFHYMT EV Micrel, MIC23250-GFHYMT EV Datasheet - Page 2

• Manufacturer Part Number: MIC23250-GFHYMT EV
• Description: Power Management IC Development Tools High Efficiency Dual 400mA Synchronous Buck Switcher - Evaluation Board
• Manufacturer: Micrel
• Type: DC/DC Converters, Regulators & Controllersr

Specifications of MIC23250-GFHYMT EV

• Product: Evaluation Boards
• Tool Is For Evaluation Of: MIC23250
• Input Voltage: 2.7 V to 5.5 V
• Output Voltage: 1.2 V, 1.8 V
• Description/function: Evaluation Board
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Output Current: 100 mA
• For Use With: MIC23250

Feedback Resistor Selection (Adjustable Only)
The feedback pins (FB1/FB2) are two extra pins that can
only be found on the MIC23250-AAYMT devices. It
allows the regulated output voltage to be set by applying
an external resistor network. The internal reference
voltage is 0.72V and the recommended value of R
is within 10% of 442kΩ. The R
from the FB pin to the output of the device and R
is the resistor from the FB pin to ground. The output
voltage is calculated from the equation below.
Compensation
The MIC23250 is designed to be stable with a 0.47µH to
4.7µH inductor with a minimum of 2.2µF ceramic (X5R)
output capacitor. For the adjustable MIC23250, the total
feedback resistance should be kept as high as possible
to reduce current loss down the feedback resistor
network. This helps to improve efficiency. A feed-forward
capacitor (CFF) of 120pF must be used in conjunction
with the external feedback resistors to reduce the effects
of parasitic capacitance that is inherent of most circuit
board layouts. Figure 1 and Table 1 shows the
recommended feedback resistor values along with the
recommended feed-forward capacitor for the MIC23250
adjustable device.
For V
R
components are: R
Micrel, Inc.
July 2009
BOTTOM
O
1 the feedback components are: R
V
OUT
= R4, C
Figure 1. Feedback Resistor Network
=
. 0
72
R
TOP
FF
TOP
V
⎛
⎜
⎜
⎝
= R5, R
R
= C5. For V
R
BOTTOM
R
TOP
BOTTOM
BOTTOM
TOP
+
C
resistor is the resistor
1
⎞
⎟
⎟
⎠
FF
= R6, C
O
2 the feedback
FF
TOP
= C6.
BOTTOM
BOTTOM
= R3,
2
Table 1. Recommended Feedback Component Values
V
OUT
0.8
0.9
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.1
3.2
3.3
1
2
3
(V)
R
TOP
1031
1093
1154
1216
1277
1338
1400
1461
1522
1584
111
172
233
295
356
417
479
540
602
663
724
786
847
909
970
49
(kΩ)
MIC23250 Evaluation Board
R
BOTTOM
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
442
(kΩ)
M9999-070909-C
CFF (pF)
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120