MIC2124
Constant Frequency, Synchronous
Current Mode Buck Controller
Hyper Speed Control™ Family
General Description
The Micrel MIC2124 is a member of the Hyper Speed
Contro™l family of DC-DC controllers. It uses an adaptive
on-time current mode control scheme and operates at a
constant frequency.
The MIC2124 operates over a supply range of +3V to
+18V, and is independent of the IC supply voltage V
IN
. It
operates at a fixed 300kHz switching frequency and can
be used to provide up to 25A of output current. The output
voltage is adjustable down to +0.8V.
The MIC2124 includes an EN/COMP pin that can be
pulled low to shut down the converter. The MIC2124
optimizes performance and ensures stability with external
compensation.
The UVLO is provided to ensure proper operation under
power-sag conditions and to make sure that the external
power MOSFET has enough voltage to work with. An
internal digital soft-start ensures reduced inrush current.
Cycle-by-cycle current limiting ensures FET protection.
The MIC2124 is available in a 10-pin MSOP package with
a junction temperature operating range from –40ºC to
+125ºC.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
+3V to +18V input voltage
25A output current capability
TM
Any Capacitor stable
-
Zero ESR to high ESR
Output down to 0.8V with ±1% FB accuracy
Up to 94% efficiency
300kHz switching frequency
All N-Channel MOSFET design
Shutdown feature with EN/COMP
No current-sense resistor needed
Internal 4ms digital soft-start
Thermal shutdown
Pre-bias output safe
Cycle-by-Cycle foldback current-limit protection
10-pin MSOP package
–40ºC to +125ºC junction temperature range
Applications
•
•
•
•
•
•
•
Printers and scanners
Graphic and video cards
PCs and servers
Microprocessor core supply
Low-voltage distributed power
Telecommunication and networking
Set-top box, gateways and router
Typical Application
12V to 3.3V Efficiency
100
90
EFFICIENCY (%)
80
70
V
HSD
= 12V
V
IN
= 5V
0
2
4
6
8
O UT PUT CURRENT (A)
10
60
MIC2124 Adjustable Output 300kHz Buck Converter
Hyper Speed Control and Any Capacitor are trademarks 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
June 2010
M9999-060810-D
Micrel, Inc.
MIC2124
Ordering Information
Part Number
MIC2124YMM
Voltage
Adj.
Switching Frequency
300kHz
Junction Temp. Range
–40° to +125°C
Package
10-Pin MSOP
Lead Finish
Pb-Free
Pin Configuration
10-Pin MSOP (MM)
Pin Description
Pin Number
1
Pin Name
HSD
Pin Function
High-Side N-MOSFET Drain Connection (Input): Input voltage for the internal sensing of external
power stage supply. The HSD operating voltage range is from 3V to 18V. Input capacitors between
HSD and the power ground (PGND) are required.
Enable (Input): Floating = enable, logic low = shutdown. In the off state, supply current of the device is
greatly reduced (typically 1mA).
COMP (Output): Output of the gm error amplifier and connects to the components for the external
compensation.
Feedback (Input): Input to the transconductance amplifier of the control loop. The FB pin is regulated
to 0.8V. A resistor divider connecting the feedback to the output is used to adjust the desired output
voltage.
Signal ground. GND is the ground path for the device input voltage V
IN
and the control circuitry. The
loop for the signal ground should be separate from the power ground (PGND) loop.
Input Voltage (Input): Power to the internal reference and control sections of the MIC2124. The IN
operating voltage range is from 3V to 5.5V. A 2.2µF ceramic capacitors from IN to GND are
recommended for clean operation. Connect IN to HSD when V
HSD
< 5.5V.
Low-Side Drive (Output): High-current driver output for external low-side MOSFET. The DL driving
voltage swings from ground-to-IN.
Power Ground. PGND is the ground path for the MIC2124 buck converter power stage. The PGND
pin connects to the sources of low-side N-Channel MOSFETs, the negative terminals of input
capacitors, and the negative terminals of output capacitors. The loop for the power ground should be
as small as possible and separate from the Signal ground (GND) loop.
High-Side Drive (Output): High-current driver output for external high-side MOSFET. The DH driving
voltage is floating on the switch node voltage (LX). It swings from V
LX
to V
BST
.
Switch Node (Input): High-current output driver return. The LX pin connects directly to the switch
node. Due to the high speed switching on this pin, the LX pin should be routed away from sensitive
nodes.
Current Sense input (Input): LX pin also senses the current for the current mode control and short
circuit protection by monitoring the voltage across the low-side MOSFET during OFF time. In order to
sense the current accurately, connect the low-side MOSFET drain to LX using a Kelvin connection.
Boost (Output): Bootstrapped voltage to the high-side N-channel MOSFET driver. A Schottky diode is
connected between the IN pin and the BST pin. A boost capacitor of 0.1μF is connected between the
BST pin and the LX pin. Adding a small resistor at BST pin can slow down the turn-on time of high-
side N-Channel MOSFETs.
2
EN/COMP
3
FB
4
5
GND
IN
6
7
DL
PGND
8
9
DH
LX
10
BST
June 2010
2
M9999-060810-D
Micrel, Inc.
MIC2124
Absolute Maximum Ratings
(1)
IN, FB to GND .................................................. -0.3V to +6V
BST to LX ......................................................... -0.3V to +6V
BST to GND ................................................... -0.3V to +35V
DH to LX.............................................-0.3V to (V
BST
+ 0.3V)
DL, COMP to GND ...............................-0.3V to (V
IN
+ 0.3V)
HSD to GND..................................................... -0.3V to 29V
PGND to GND ............................................... -0.3V to +0.3V
(3)
Power Dissipation T
A
=70°C ................... Internally Limited
Storage Temperature (T
S
)..........................-65°C to +150°C
Lead Temperature (soldering, 10sec) ........................ 260°C
Operating Ratings
(2)
Input Voltage (V
IN
) ............................................ 3.0V to 5.5V
Supply Voltage (V
HSD
) ....................................... 3.0V to 18V
Ambient Temperature (T
A
) ...........................-40°C to +85°C
Junction Temperature (T
J
) .........................-40°C to +125°C
Junction Thermal Resistance MSOP (θ
JA
) ............130°C/W
Junction Thermal Resistance MSOP (θ
JC
) ..............43°C/W
Electrical Characteristics
(5)
V
HSD
= 13.2V, V
IN
= 5V, V
BST
- V
LX
= 5V; T
A
= 25°C, unless noted.
Bold
values indicate -40°C
≤
T
A
≤
+85°C.
Parameter
General
Operating Input Voltage (V
IN
)
HSD Voltage Range (V
HSD
)
Quiescent Supply Current
Shutdown Current
Under-Voltage Lockout
Under-voltage Lockout Trip Level
UVLO Hysteresis
DC-DC Controller
Output-Voltage Adjust Range
(V
OUT
)
Error Amplifier
FB Regulation Voltage
FB Regulation Voltage
Transconductance g
m
COMP Output Voltage Swing
FB Input Leakage Current
On Timer
Switching Frequency
Maximum Duty Cycle
Minimum Duty Cycle
Short Current Protection
Current Limit 1
Current Limit 2
V
FB
= 0.8V
V
FB
= 0V
110
21
127
36
145
51
mV
mV
V
HSD
= 4V, V
IN
= 5V, V
LX
= 3.33V
FB > 0.8V
240
89
300
91
0
360
93
kHz
%
%
V
FB
= 0.8V
0°C
≤
T
A
≤
85°C
-40°C
≤
T
A
≤
85°C
-1
-2.5
70
0.5
1
±0.2
±0.2
110
1
1
160
2.3
500
%
%
µS
V
nA
Depends on external components and the
maximum duty cycle.
0.8
V
Rising edge
2.5
2.7
40
2.93
V
mV
V
FB
= 1.5V
V
EN/COMP
= GND
(6)
Conditions
Min
3.0
3.0
Typ
Max
5.5
18
Units
V
V
mA
mA
1.4
1
2
2
June 2010
3
M9999-060810-D
Micrel, Inc.
Parameter
FET Drivers
DH, DL Output Low Voltage
DH, DL Output High Voltage
DH On-Resistance, High State
DH On-Resistance, Low State
DL On-Resistance, High State
DL On-Resistance, Low State
LX, BST, HSD Leakage Current
Thermal Protection
Over-temperature Shutdown
Over-temperature Shutdown
Hysteresis
Shutdown Control
EN/COMP Logic Level High
EN/COMP Logic Level Low
EN/COMP Hysteresis
EN/COMP Pull-up Current
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
MIC2124
Conditions
I
SINK
= 10mA
I
SOURCE
= 10mA, measured the difference
between V
BST
-V
DH
, V
IN
-V
DL
0.1
2
1.5
2
1
T
A
= 25°C
160
5
3
3
3
2
30
Min
Typ
Max
0.1
Units
V
V
Ω
Ω
Ω
Ω
µA
°C
°C
3V < V
IN
<5.5V
3V < V
IN
<5.5V
3V < V
IN
<5.5V
V
EN/COMP
= 0V
0.5
0.4
0.4
26
47
100
0.25
V
V
mV
µA
3. The maximum allowable power dissipation of any T
A
is P
D(max)
= (T
J(max)
-T
A
) /
θ
JA
. Exceeding the maximum allowable power dissipation will result in
excessive die temperature, and the regulator will go into thermal shutdown.
4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
5. Specification for packaged product only.
6. The application is fully functional at low IN (supply of the control section) if the external MOSFETs have enough low voltage V
TH
.
June 2010
4
M9999-060810-D
Micrel, Inc.
MIC2124
Typical Characteristics
Efficiency
vs. Load Current
100
Output Voltage
vs. Load Current
2.60
Output Voltage Change
vs. Input Voltage
70
OUTPUT VOTLAGE CHANGE(mV)
50
V
OUT =
2.5V
90
80
70
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
2.55
V
OUT
= 2.5V
30
10
-10
-30
-50
-70
V
OUT
= 1.5V
60
50
40
0.1
1.0
LOAD CURRENT (A)
10.0
2.50
V
IN
= V
HSD
= 5V
2.45
V
OUT
= 0.8V
V
IN
= V
HSD
I
OUT
= 5A
V
IN
= V
HSD
= 5V
2.40
0
1
2
3
LOAD CURRENT (A)
4
5
3.0
3.5
4.0
4.5
5.0
INPUT VOTLAGE (V)
5.5
Output Voltage
vs. Input Voltage
0.810
Switching Frequency
vs. Input Voltage
350
SWITCHING FREQUENCY (kHz)
OUTPUT VOTLAGE (V)
0.805
330
310
-40°C
25°C
0.800
290
0.795
270
85°C
V
IN
= VHSD
V
OUT
= 1.8V
I
OUT
= 2.5A
I
OUT
= 5A
0.790
10.8
250
11.4
12.0
12.6
INPUT VOTLAGE (V)
13.2
3.0
3.5
4.0
4.5
5.0
INPUT VOTLAGE (V)
5.5
June 2010
5
M9999-060810-D
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