MIC2168A Micrel Semiconductor, MIC2168A Datasheet

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MIC2168A

Manufacturer Part Number
MIC2168A
Description
1MHz PWM Synchronous Buck Control IC
Manufacturer
Micrel Semiconductor
Datasheet
General Description
The MIC2168A is a high-effi ciency, simple to use 1MHz PWM
synchronous buck control IC housed in a small MSOP-10
package. The MIC2168A allows compact DC/DC solutions
with a minimal external component count and cost.
The MIC2168A operates from a 3V to 14.5V input, without
the need of any additional bias voltage. The output voltage
can be precisely regulated down to 0.8V. The adaptive all
N-Channel MOSFET drive scheme allows effi ciencies over
95% across a wide load range.
The MIC2168A senses current across the high-side N-
Channel MOSFET, eliminating the need for an expensive
and lossy current-sense resistor. Current limit accuracy is
maintained by a positive temperature coeffi cient that tracks
the increasing R
and space are saved by the internal in-rush-current limiting
and space are saved by the internal in-rush-current limiting
digital soft-start.
The MIC2168A is available in a 10-pin MSOP package, with
a wide junction operating range of –40°C to +125°C.
All support documentation can be found on Micrel’s web site
at www.micrel.com.
Typical Application
April 2005
100pF
V
100µF
www.DataSheet4U.com
IN
= 5V
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
4kΩ
100nF
MIC2168A Adjustable Output 1MHz Converter
DS(ON)
DS(ON)
DS(ON)
VIN
COMP/EN
VDD
MIC2168A
GND
4.7µF
of the external MOSFET. Further cost
BST
VSW
HSD
LSD
FB
CS
SD103BWS
1000nF
2Ω
0.1µF
1kΩ
IRF7821
IRF7821
1.2µH
1
10kΩ
3.24kΩ
Features
• 3V to 14.5V input voltage range
• Adjustable output voltage down to 0.8V
• Up to 95% effi ciency
• 1MHz PWM operation
• Adjustable current-limit senses high-side N-Channel
• No external current sense resistor
• Adaptive gate drive increases effi ciency
• Ultra-fast response with hysteretic transient recovery
• Overvoltage protection protects the load in fault
• Dual mode current limit speeds up recovery time
• Hiccup mode short-circuit protection
• Internal soft-start
• Dual function COMP and EN pin allows low-power shut-
• Small size MSOP 10-lead package
Applications
• Point-of-load DC/DC conversion
• Set-top boxes
• Graphic cards
• LCD power supplies
• Telecom power supplies
• Networking power supplies
• Cable modems and routers
MOSFET current
mode
conditions
down
1MHz PWM Synchronous Buck Control IC
150µF x 2
3.3V
MIC2168A
MIC2168A
100
95
90
85
80
75
70
65
60
55
50
0
MIC2168 Efficiency
2
I
4
LOAD
(A)
V
V
6
IN
OUT
= 5V
= 3.3V
8
M9999-062205
10

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MIC2168A Summary of contents

Page 1

... General Description The MIC2168A is a high-effi ciency, simple to use 1MHz PWM synchronous buck control IC housed in a small MSOP-10 package. The MIC2168A allows compact DC/DC solutions with a minimal external component count and cost. The MIC2168A operates from 14.5V input, without the need of any additional bias voltage. The output voltage can be precisely regulated down to 0.8V. The adaptive all N-Channel MOSFET drive scheme allows effi ...

Page 2

... MIC2168A Ordering Information Part Number Standard Pb-Free MIC2168ABMM MIC2168AYMM www.DataSheet4U.com Pin Confi guration Pin Description Pin Number Pin Number Pin Number Pin Number Pin Name Pin Name Pin Name Pin Name VIN VIN VIN VDD VDD VDD ...

Page 3

... MIC2168A Absolute Maximum Ratings Supply Voltage (V ) ................................................... 15.5V IN Booststrapped Voltage (V ) .................................V BST Junction Temperature (T ) ...................–40°C ≤ www.DataSheet4U.com Storage Temperature (T ) ........................ –65°C to +150 °C S Electrical Characteristics T = 25° 5V, unless otherwise specifi ed. Bold values indicate –40°C < Parameter ...

Page 4

... MIC2168A Electrical Characteristics Parameter Parameter Parameter Parameter Parameter Parameter Condition Condition Condition Condition Condition Condition Error Amplifi Gain DC Gain DC Gain DC Gain DC Gain DC Gain www.DataSheet4U.com Transconductance Transconductance Transconductance Transconductance Transconductance Transconductance Soft-Start Soft-Start Current Soft-Start Current After timeout of internal timer. See After timeout of internal timer. See “ ...

Page 5

... MIC2168A Typical Characteristics PWM Mode Supply Current www.DataSheet4U.com vs. Temperature 2.9 2.7 2.5 2.3 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 0.5 -40 - 100 120 140 TEMPERATURE (°C) V vs. Temperature FB 0.820 0.815 0.810 0.805 0.800 0.795 0.790 0.785 0.780 -60 - 120 150 TEMPERATURE (°C) V Line Regulation DD vs. Temperature 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -60 -30 ...

Page 6

... This will cause the PWM comparator to increase t the top side MOSFET, causing the output voltage and bringing V Soft-Start The COMP/EN pin on the MIC2168A is used for the following three functions: 1. Disables the part by grounding this pin 2. External compensation to stabilize the voltage control loop 3 ...

Page 7

... MOSFET Gate Drive The MIC2168A high-side drive circuit is designed to switch an N-Channel MOSFET. The block diagram in Figure 2 shows a bootstrap circuit, consisting of D2 and CBST, supplies energy to the high-side drive circuit. Capacitor CBST is charged while the low-side MOSFET is on and the voltage on the VSW pin is approximately 0V ...

Page 8

... G[low G[low -side](avg) side](avg) ISS ISS ISS GS GS Since the current from the gate drive comes from the input voltage, the power dissipated in the MIC2168A due to gate drive is ...

Page 9

... Maximizing effi ciency requires the proper selection of core material and minimizing the winding resistance. The high frequency operation of the MIC2168A requires the use of ferrite materials for all but the most cost sensitive applica- tions. Lower cost iron powder cores may be used but the increase in core loss will reduce the effi ...

Page 10

... ESR (rms) C (rms) C (rms) www.DataSheet4U.com IN IN Voltage Setting Components The MIC2168A requires two resistors to set the output volt- age as shown in Figure 2. Error Amp V REF 0.8V MIC2168 [adj.] Figure 2. Voltage-Divider Confi guration Where: V for the MIC2168A is typically 0.8V REF The output voltage is determined by the equation:  ...

Page 11

... Figure 4, versus 105° for Figure 6. The simple RC and C2 compensation scheme allows a maximum error amplifi er phase boost of about 90°. Therefore easier to stabilize the MIC2168A voltage control loop by using high ESR value output capacitors. g Error Amplifi undesirable to have high error amplifi ...

Page 12

... Figure 8. Error Amplifi er Phase Curve Total Open-Loop Response The open-loop response for the MIC2168A controller is easily obtained by adding the power path and the error amplifi er gains together, since they already are in Log scale desirable to have the gain curve intersect zero dB at tens of kilohertz, this is commonly called crossover frequency ...

Page 13

... The compensation resistor and capacitors should be placed right next to the COMP/EN pin and the other side should connect directly to the GND pin on the MIC2168A rather than going to the plane. 5. The input bulk capacitors should be placed close to the drain of the top MOSFET. ...

Page 14

... MIC2168A Package Information www.DataSheet4U.com MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA + 1 (408) 944-0800 TEL 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 specifi cations at any time without notifi cation to the customer. ...

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