MIC2164-2YMM Micrel Inc, MIC2164-2YMM Datasheet - Page 18

• Manufacturer Part Number: MIC2164-2YMM
• Description: IC PWM BUCK CNTLLR 10MSOP
• Manufacturer: Micrel Inc
• Series: Hyper Speed Control™r
• Type: Step-Down (Buck)r

Specifications of MIC2164-2YMM

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 ~ 5.5 V
• Frequency - Switching: 600kHz
• Voltage - Input: 3 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Voltage - Supply: 3 V ~ 28 V
• Frequency-max: 750kHz
• Duty Cycle: 74%
• Pwm Type: Controller
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-3543-5

Micrel, Inc.
R
where:
T
T
R
(usually specified by the manufacturer)
Output Capacitor Selection
The type of the output capacitor is usually determined by
its ESR (equivalent series resistance). Voltage and RMS
current capability are two other important factors for
selecting the output capacitor. Recommended capacitors
are tantalum, low-ESR aluminum electrolytic, OS-CON
and POSCAPS. The output capacitor’s ESR is usually
the main cause of the output ripple. The output capacitor
ESR also affects the control loop from a stability point of
view. The maximum value of ESR is calculated:
where:
Δ V
ΔI
The total output ripple is a combination of the ESR and
output capacitance. The total ripple is calculated below:
where:
D = duty cycle
C
f
As described in the “Theory of Operation” subsection in
“Functional Description”, MIC2164/-2/-3 requires at least
20mV peak-to-peak ripple at the FB pin to make the g
amplifier and the error comparator to behavior properly.
Also, the output voltage ripple should be in phase with
the inductor current. Therefore, the output voltage ripple
caused by the output capacitor C
smaller than the ripple caused by the output capacitor
ESR. If low ESR capacitors are selected as the output
capacitors, such as ceramic capacitors, a ripple injection
method is applied to provide the enough FB voltage
ripples. Please refer to the “Ripple Injection” subsection
for more details.
SW
September 2010
H
20°C
WINDING
WINDING(20°C)
OUT
L(PP)
OUT(pp)
= temperature of wire under full load
ΔV
= switching frequency
= output capacitance value
= ambient temperature
= peak-to-peak inductor current ripple
OUT(pp)
= R
= peak-to-peak output voltage ripple
WINDING(20°c)
ESR
=
= room temperature winding resistance
⎛
⎜
⎜
⎝
C
C
OUT
OUT
ΔI
≤
× (1 + 0.0042 × (T
L(PP)
⋅
ΔV
f
ΔI
SW
OUT(pp)
L(PP)
⋅
8
⎞
⎟
⎟
⎠
2
+
OUT
(
ΔI
L(PP)
should be much
H
– T
⋅
ESR
20°C
)) (17)
C
OUT
(18)
(19)
)
2
m
18
The voltage rating of the capacitor should be twice the
output voltage for a tantalum and 20% greater for
aluminum electrolytic or OS-CON. The output capacitor
RMS current is calculated below:
The power dissipated in the output capacitor is:
Input Capacitor Selection
The input capacitor for the power stage input V
should be selected for ripple current rating and voltage
rating. Tantalum input capacitors may fail when
subjected to high inrush currents, caused by turning the
input supply on. A tantalum input capacitor’s voltage
rating should be at least two times the maximum input
voltage to maximize reliability. Aluminum electrolytic,
OS-CON, and multilayer polymer film capacitors can
handle the higher inrush currents without voltage de-
rating. The input voltage ripple will primarily depend
upon the input capacitor’s ESR. The peak input current
is equal to the peak inductor current, so:
The input capacitor must be rated for the input current
ripple. The RMS value of input capacitor current is
determined at the maximum output current. Assuming
the peak-to-peak inductor current ripple is low:
The power dissipated in the input capacitor is:
P
I
CIN
DISS(CIN)
(
RMS
I
P
Δ
)
C
= I
DISS(C
V
OUT
≈
IN
CIN(RMS)
I
OUT
(RMS)
=
OUT
I
( L
(max)
)
PK
=
2
×ESR
=
ΔI
)
I
C
×
×
L(PP)
12
OUT
ESR
D
CIN
(RMS)
×
CIN
(
1
2
−
⋅
D
ESR
)
MIC2164/-2/-3/C
M9999-091310-D
C
OUT
(20)
(21)
(22)
(23)
(24)
HSD