MIC26400
5A Hyper Speed Control
TM
Synchronous DC/DC Buck Regulator
SuperSwitcher II
TM
General Description
The Micrel MIC26400 is a constant-frequency, synchronous
buck regulator featuring a unique digitally modified adaptive
ON-time control architecture. The MIC26400 operates over
an input supply range of 4.5V to 26V and provides a
regulated output at up to 5A 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 MIC26400 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, foldback 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
Output down to 0.8V with ±1% accuracy
Any Capacitor
TM
Stable
-
Zero ESR to high-ESR output capacitance
5A 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
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 2010
M9999-070110-A
Micrel, Inc.
MIC26400
Ordering Information
Part Number
MIC26400YJL
Voltage
Adjustable
Switching Frequency
300kHz
Junction Temperature
Range
–40°C to +125°C
Package
28-Pin 5mm X 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
Pin Name
PVIN
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 the PVIN pins and the power ground (PGND) are required.
Note that the connection must be kept short.
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, the V
DD
supply current of the device is
reduced (typically 0.7mA).
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. (see
PCB Layout Guidelines
for details.)
V
DD
Bias (Input): Power to the internal reference and control sections of the MIC26400. The V
DD
operating voltage range is from 4.5V to 5.5V. A 2.2µF ceramic capacitor from the VDD pin-to-PGND
must be placed next to the IC.
Power Ground. PGND is the ground path for the MIC26400 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.
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.
EN
25
26
27
FB
SGND
VDD
2, 5, 6, 7, 8, 21
PGND
22
CS
20
4, 9, 10, 11, 12
23
1, 3, 28
BST
SW
VIN
NC
July 2010
2
M9999-070110-A
Micrel, Inc.
MIC26400
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
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
)
Under-Voltage 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
Oscillator
Switching Frequency
Minimum duty cycle
Minimum Off-time
Soft-Start
Soft-Start time
6
ms
(6)
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 5A
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
225
V
FB
= 0V
V
FB
> 0.8V
1.2
0.792
0.788
2.4
5
2.7
50
1.4
0.7
26
5.5
3.2
3
2
V
V
V
mV
mA
mA
0.8
0.8
0.2
0.1
5
0.85
0.78
50
300
87
0
360
0.808
0.812
V
%
%
nA
V
0.4
V
µA
375
kHz
%
%
ns
Maximum duty cycle
(7)
July 2010
3
M9999-070110-A
Micrel, Inc.
MIC26400
Electrical Characteristics
(5)
(Continued)
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
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:
1. Exceeding the absolute maximum rating may damage the device.
2. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
3. The device is not guaranteed to function outside operating range.
4. PD
(MAX)
= (T
J(MAX)
– T
A
)/
θ
JA
, where
θ
JA
depends upon the printed circuit layout. See “Applications Information.”
5. Specification for packaged product only.
6. Measured in test mode.
7. The maximum duty-cycle is limited by the fixed mandatory off-time t
OFF
of typically 360ns.
Condition
Min.
Typ.
Max.
Units
V
FB
= 0.8V
V
FB
= 0V
I
SW
= 1A
I
SW
= 1A
V
IN
= 26V, V
SW
= 26V, V
EN
= 0V, V
BST
= 31.5 V
V
IN
= 26V, V
SW
= 0V, V
EN
= 0V, V
BST
= 31.5V
T
J
Rising
6
13
6
43
12.5
60
25
155
10
A
A
mΩ
mΩ
µA
µA
°C
°C
July 2010
4
M9999-070110-A
Micrel, Inc.
MIC26400
Typical Characteristics
V
IN
Operating Supply Current
vs. Input Voltage
10.0
SHUTDOWN CURRENT (µA)
SUPPLY CURRENT (mA)
8.0
6.0
4.0
V
OUT
= 1.2V
V
IN
Shutdown Current
vs. Input Voltage
20
16
12
8
4
0
V
DD
= 5V
V
EN
= 0V
V
DD
Operating Supply Current
vs. Input Voltage
10
SUPPLY CURRENT (mA)
8
6
4
V
OUT
= 1.2V
2.0
0.0
4
10
16
I
OUT
= 0A
V
DD
= 5V
SWITCHING
2
0
V
DD
= 5V
SWITCHING
22
28
4
10
16
22
28
4
10
16
22
28
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Feedback Voltage
vs. Input Voltage
0.808
FEEDBACK VOLTAGE (V)
TOTAL REGULATION (%)
1.0%
0.8%
0.6%
0.4%
0.2%
0.0%
4
10
16
22
28
4
Total Regulation
vs. Input Voltage
20
V
OUT
= 1.2V
Current Limit
vs. Input Voltage
0.804
CURRENT LIMIT (A)
V
DD
= 5V
I
OUT
= 0A to 5A
15
0.800
10
0.796
V
OUT
= 1.2V
V
DD
= 5V
I
OUT
= 0A
5
V
OUT
= 1.2V
V
DD
= 5V
0.792
INPUT VOLTAGE (V)
0
10
16
22
28
4
10
16
22
28
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Switching Frequency
vs. Input Voltage
390
SWITCHING FREQUENCY (kHz)
V
OUT
= 1.2V
345
V
DD
= 5V
I
OUT
= 0A
300
255
210
4
10
16
22
28
INPUT VOLTAGE (V)
July 2010
5
M9999-070110-A
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