MIC26950
12A Hyper Speed Control
TM
Synchronous DC-DC Buck Regulator
SuperSwitcher II
TM
General Description
The Micrel MIC26950 is a constant-frequency, synchronous
buck regulator featuring a unique digitally modified adaptive
ON-time control architecture. The MIC26950 operates over
an input supply range of 4.5V to 26V and provides a
regulated output at up to 12A of output current. The output
voltage is adjustable down to 0.8V with a typical accuracy of
±1%, and the device operates at a switching frequency of
300kHz.
Micrel’s Hyper Speed Control
TM
architecture allows for ultra-
fast transient response while reducing the output capacitance
and also makes (High V
IN
)/(Low V
OUT
) operation possible.
This digitally modified adaptive t
ON
ripple control architecture
combines the advantages of fixed-frequency operation and
fast transient response in a single device.
The MIC26950 offers a full suite of protection features to
ensure protection of the IC during fault conditions. These
include undervoltage lockout to ensure proper operation
under power-sag conditions, internal soft-start to reduce
inrush current, fold-back current limit, “hiccup” mode short-
circuit protection and thermal shutdown.
All support documentation can be found on Micrel’s web
site at:
www.micrel.com.
Features
•
Hyper Speed Control
TM
architecture enables
-
High delta V operation (V
IN
= 26V and V
OUT
= 0.8V)
-
Small output capacitance
4.5V to 26V input voltage
Adjustable output from 0.8V to 5.5V (±1% accuracy)
Any Capacitor
TM
Stable
-
Zero-ESR to high-ESR output capacitance
12A output current capability
300kHz switching frequency
Internal compensation
Up to 95% efficiency
6ms internal soft-start
Foldback current-limit and “hiccup” mode short-circuit
protection
Thermal shutdown
Supports safe start-up into a pre-biased load
–40°C to +125°C junction temperature range
28-pin 5mm X 6mm MLF
®
package
•
•
•
•
•
•
•
•
•
•
•
•
•
Applications
•
Distributed power systems
•
Communications/networking infrastructure
•
Set-top box, gateways and routers
•
Printers, scanners, graphic cards and video cards
____________________________________________________________________________________________________________
Typical Application
100
95
EFFICIENCY (%)
90
85
80
75
70
65
60
0
3
6
9
12
15
Efficiency (V
IN
= 12V)
vs. Output Current
5.0V
3.3V
2.5V
1.5V
1.0V
OUTPUT CURRENT (A)
Hyper Speed Control, SuperSwitcher II and Any Capacitor are trademarks of Micrel, Inc.
MLF and
MicroLeadFrame
are registered trademarks of Amkor Technology, 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
July 2011
M9999-070111-C
Micrel, Inc.
MIC26950
Ordering Information
Part Number
MIC26950YJL
Voltage
Adjustable
Switching Frequency
300kHz
Junction Temperature
Range
–40°C to +125°C
Package
28-pin 5mm
×
6mm MLF
®
Lead Finish
Pb-Free
Pin Configuration
28-Pin 5mm X 6mm MLF
®
(YJL)
Pin Description
Pin
Number
13,14,15,
16,17,18,
19
24
EN
PVIN
Pin Name
Pin Function
High-Side N-internal MOSFET Drain Connection (Input): The PV
IN
operating voltage range is from
4.5V to 26V. Input capacitors between PV
IN
and the power ground (PGND) are required.
Enable (Input): A logic level control of the output. The EN pin is CMOS-compatible. Logic high or
floating = enable, logic low = shutdown. In the off state, supply current of the device is greatly reduced
(typically 0.8mA).
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. SGND must be connected directly to the ground planes. Do not route the SGND pin to
the PGND Pad on the top layer.
V
DD
Bias (Input): Power to the internal reference and control sections of the MIC26950. The V
DD
operating voltage range is from 4.5V to 5.5V. A 2.2µF ceramic capacitor from the VDD pin-to-PGND is
recommended for clean operation.
Power Ground. PGND is the ground path for the MIC26950 buck converter power stage. The PGND
pin connects to the sources of low-side N-Channel internal 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 (SGND) loop.
Current Sense (Input): High current output driver return. The CS pin connects directly to the switch
node. Due to the high speed switching on this pin, the CS pin should be routed away from sensitive
nodes. CS pin also senses the current by monitoring the voltage across the low-side internal
MOSFET during OFF-time.
25
26
27
FB
SGND
VDD
2, 5, 6,
7, 8, 21
PGND
22
CS
July 2011
2
M9999-070111-C
Micrel, Inc.
MIC26950
Pin Description (Continued)
Pin
Number
20
4, 9, 10,
11, 12
23
1, 3, 28
Pin Name
BST
SW
VIN
NC
Pin Function
Boost (Output): Bootstrapped voltage to the high-side N-channel internal MOSFET driver. A Schottky
diode is connected between the VDD pin and the BST pin. A boost capacitor of 0.1μF is connected
between the BST pin and the SW pin.
Switch Node (Output): Internal connection for the high-side MOSFET source and low-side MOSFET
drain.
Power Supply Voltage (Input): Requires bypass capacitor to SGND.
No Connect.
July 2011
3
M9999-070111-C
Micrel, Inc.
MIC26950
Absolute Maximum Ratings
(1,2)
PV
IN
to PGND................................................
−0.3V
to +28V
V
IN
to PGND ....................................................−0.3V to PV
IN
V
DD
to PGND ...................................................
−0.3V
to +6V
V
SW
, V
CS
to PGND ..............................
−0.3V
to (PV
IN
+0.3V)
V
BST
to V
SW
........................................................
−0.3V
to 6V
V
BST
to PGND ..................................................
−0.3V
to 34V
V
EN
to PGND ......................................
−0.3V
to (V
DD
+ 0.3V)
V
FB
to PGND.......................................
−0.3V
to (V
DD
+ 0.3V)
PGND to SGND ...........................................
−0.3V
to +0.3V
Junction Temperature .............................................. +150°C
Storage Temperature (T
S
).........................−65°C to +150°C
Lead Temperature (soldering, 10sec)........................ 260°C
Operating Ratings
(3)
Supply Voltage (PV
IN
, V
IN
)............................... 4.5V to 26V
Output Voltage Range (V
OUT
)........................... 0.8V to 5.5V
Bias Voltage (V
DD
)............................................ 4.5V to 5.5V
Enable Input (V
EN
) ................................................. 0V to V
DD
Junction Temperature (T
J
) ........................
−40°C
to +125°C
Maximum Power Dissipation......................................Note 4
Package Thermal Resistance
(4)
5mm x 6mm MLF
®
(θ
JA
) .....................................36°C/W
Electrical Characteristics
(5)
PV
IN
= V
IN
= 12V, V
DD
= 5V; V
BST
– V
SW
= 5V; T
A
= 25°C, unless noted.
Bold
values indicate
−40°C
≤
T
J
≤
+125°C.
Parameter
Power Supply Input
Input Voltage Range (V
IN
, PV
IN
)
V
DD
Bias Voltage
Operating Bias Voltage (V
DD
)
Undervoltage Lockout Trip Level
UVLO Hysteresis
Quiescent Supply Current
Shutdown Supply Current
Reference
Feedback Reference Voltage
Load Regulation
Line Regulation
FB Bias Current
Enable Control
EN Logic Level High
EN Logic Level Low
EN Bias Current
Notes:
1.
2.
3.
4.
5.
Exceeding the absolute maximum rating may damage the device.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
The device is not guaranteed to function outside operating range.
PD
(MAX)
= (T
J(MAX)
– T
A
)/
θ
JA
, where
θ
JA
depends upon the printed circuit layout. See “Applications Information.”
Specification for packaged product only.
Condition
Min.
Typ.
Max.
Units
4.5
4.5
V
DD
Rising
V
FB
= 1.5V
V
DD
= V
BST
= 5.5V, V
IN
= 26V
SW = unconnected, V
EN
= 0V
0°C
≤T
J
≤
85°C (±1.0%)
−40°C
≤T
J
≤
125°C (±1.5%)
I
OUT
= 0A to 12A
V
IN
= (V
OUT
+ 3.0V) to 26V
V
FB
= 0.8V
4.5V < V
DD
< 5.5V
4.5V < V
DD
< 5.5V
V
EN
= 0V
1.2
0.792
0.788
0.8
0.8
0.2
0.1
5
0.85
0.78
50
2.4
5
2.7
50
1.4
0.7
26
5.5
3.2
3
2
V
V
V
mV
mA
mA
0.808
0.812
V
%
%
nA
V
0.4
V
µA
July 2011
4
M9999-070111-C
Micrel, Inc.
MIC26950
Electrical Characteristics
(5)
PV
IN
= V
IN
= 12V, V
DD
= 5V; V
BST
– V
SW
= 5V; T
A
= 25°C, unless noted.
Bold
values indicate
−40°C
≤
T
J
≤
+125°C.
Parameter
Oscillator
Switching Frequency
(6)
Maximum Duty Cycle
Minimum Duty Cycle
Minimum Off-Time
Soft-Start
Soft-Start Time
Short-Circuit Protection
Current-Limit Threshold
Short-Circuit Current
Internal FETs
Top-MOSFET R
DS (ON)
Bottom-MOSFET R
DS (ON)
SW Leakage Current
V
IN
Leakage Current
Thermal Protection
Over-temperature Shutdown
Over-temperature Shutdown
Hysteresis
Notes:
6.
7.
Measured in test mode.
The maximum duty-cycle is limited by the fixed mandatory off-time t
OFF
of typically 360ns.
(7)
Condition
Min.
225
Typ.
300
87
0
360
6
Max.
375
Units
kHz
%
%
ns
ms
V
FB
= 0V
V
FB
> 0.8V
V
FB
= 0.8V
V
FB
= 0V
I
SW
= 1A
I
SW
= 1A
PV
IN
= 26V, V
SW
= 26V, V
EN
= 0V, V
BST
= 31.5 V
PV
IN
= 26V, V
SW
= 0V, V
EN
= 0V, V
BST
= 31.5V
T
J
Rising
13.2
27
8
17
6
60
25
155
10
A
A
mΩ
mΩ
µA
µA
°C
°C
July 2011
5
M9999-070111-C
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