MIC28510
75V/4A Hyper Speed Control
Synchronous DC/DC Buck Regulator
SuperSwitcher II
General Description
The Micrel MIC28510 is an adjustable–frequency,
synchronous buck regulator featuring unique adaptive on–
time control architecture. The MIC28510 operates over an
input supply range of 4.5V to 75V and provides a regulated
output of up to 4A of output current. The output voltage is
adjustable down to 0.8V with a guaranteed accuracy of ±1%.
Micrel’s Hyper Speed Control architecture allows for ultra–
fast transient response while reducing the output capacitance
and also makes (High V
IN
) / (Low V
OUT
) operation possible.
This adaptive t
ON
ripple control architecture combines the
advantages of fixed–frequency operation and fast transient
response in a single device.
The MIC28510 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 architecture enables:
High Delta V operation (V
IN
= 75V and V
OUT
= 0.8V)
Small output capacitance
4.5V to 75V voltage input
4A output current capability, up to 95% efficiency
Adjustable output voltage form 0.8V to 24V
±1% FB accuracy
Any Capacitor stable:
Zero-ESR to high–ESR output capacitors
100kHz to 500kHz switching frequency
Internal compensation
Foldback current–limit and “hiccup” mode short-circuit
protection
Thermal shutdown
Supports safe startup into a pre–biased load
–40C to +125C junction temperature range
28-pin 5mm
6mm MLF
®
package
Applications
Distributed power systems
Communications/networking infrastructure
Industrial power
Solar energy
___________________________________________________________________________________________________________
Typical Application
Efficiency (V
IN
= 48V)
vs. Output Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1
2
3
4
f
SW
= 250kHz
5.0V
3.3V
2.5V
1.8V
1.5V
1.2V
1.0V
0.8V
5
6
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
March 2012
M9999-030912-A
Micrel, Inc.
MIC28510
Ordering Information
Part Number
MIC28510YJL
Junction Temperature Range
40C
to
125C
Package
28-pin 5mm
6mm MLF
®
Lead Finish
Pb-Free
Pin Configuration
28-Pin 5mm
6mm MLF
®
(JL)
Pin Description
Pin Number
1, 3
2, 5, 6,
7, 8, 21
4, 9, 10,
11, 12
13, 14, 15, 16,
17, 18, 19
20
Pin Name
NC
PGND
Pin Function
No Connect.
Power Ground. PGND is the ground path for the MIC28510 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.
Switch Node (Output). Internal connection for the high-side MOSFET source and low-side
MOSFET drain.
High-Side Internal N-Channel MOSFET Drain Connection (Input).The PVIN operating voltage
range is from 4.5V to 75V. Input capacitors between the PVIN pins and the power ground (PGND)
are required and keep the connection short.
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.
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.
SW
PVIN
BST
22
CS
March 2012
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M9999-030912-A
Micrel, Inc.
MIC28510
Pin Description (Continued)
Pin Number
23
24
Pin Name
FS
EN
Pin Function
Frequency Setting Pin.
Enable (Input). A logic level control of the output. The EN pin is CMOS-compatible. Logic high =
enable, logic low = shutdown. In the off state, the V
DD
supply current of the device is reduced
(typically 0.7mA). Do not pull the EN pin above the V
DD
supply. This pin has 100k pull-up resistor to
VDD.
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.
VDD Bias (Input). Power to the internal reference and control sections of the MIC28510. The VDD
operating voltage range is from 4.5V to 5.5V. A 2.2µF ceramic capacitor from the VDD pin to the
PGND pin must be placed next to the IC. VDD must be powered up at the same time or after PVIN
to make the soft-start function correctly.
Power Supply for Gate Driver of Bottom MOSFET.
25
26
FB
SGND
27
28
VDD
PVDD
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M9999-030912-A
Micrel, Inc.
MIC28510
Absolute Maximum Ratings
(1)
PV
IN
to PGND................................................
0.3V
to +76V
FS to PGND ....................................................0.3V to PV
IN
PV
DD
, 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 82V
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 (T
J
) ....................................... +150°C
Storage Temperature (T
S
).........................65C to +150C
Lead Temperature (soldering, 10s)............................ 260°C
ESD Rating
(2)
..............................................................1000V
Operating Ratings
(3)
Supply Voltage (PV
IN
) ....................................... 4.5V to 75V
Bias Voltage (PV
DD
, V
DD
).................................. 4.5V to 5.5V
Enable Input (V
EN
) ................................................. 0V to V
DD
Junction Temperature (T
J
) ........................
40C
to +125C
Maximum Power Dissipation......................................Note 4
Package Thermal Resistance
(4)
5mm x 6mm MLF
®
(
JA
) ....................................36C/W
Electrical Characteristics
(5)
PV
IN
= V
FS
= 48V, 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 ( PV
IN
)
FS Voltage Range
V
DD
Bias Voltage
Operating Bias Voltage (V
DD
)
Undervoltage Lockout Trip Level
UVLO Hysteresis
Quiescent Supply Current (I
VDD
)
Shutdown Supply Current (I
VDD
)
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
)/
JA
, where
JA
depends upon the printed circuit layout. See “Applications Information.”
Specification for packaged product only.
Condition
Min.
Typ.
Max.
Units
4.5
2
4.5
V
DD
Rising
V
FB
= 1.5V
V
DD
= V
BST
= 5.5V, V
IN
= 48V
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 4A
PV
IN
= 4.5 to 75V
V
FB
= 0.8V
4.5V < V
DD
< 5.5V
4.5V < V
DD
< 5.5V
V
EN
= 0V
50
-0.5
1.2
0.792
0.788
3.2
5
3.85
380
1.4
0.7
75
75
5.5
4.45
3
2
V
V
V
V
mV
mA
mA
0.8
0.8
0.04
0.1
0.005
0.808
0.812
V
%
%
0.5
µA
V
0.4
100
V
µA
March 2012
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M9999-030912-A
Micrel, Inc.
MIC28510
Electrical Characteristics
(5)
(Continued)
PV
IN
= V
FS
= 48V, 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
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
PV
IN
Leakage Current
Thermal Protection
Over–Temperature Shutdown
Over–Temperature Shutdown
Hysteresis
Note:
6.
The maximum duty–cycle is limited by the fixed mandatory off-time (t
OFF
) of typically 360ns.
(6)
Condition
V
FS
= PV
IN
V
FB
= 0V, V
FS
=PV
IN
V
FB
> 0.8V
Min.
375
Typ.
500
80
0
360
6
Max.
625
Units
kHz
%
%
ns
ms
V
FB
= 0.8V, T
J
= 25°C
V
FB
= 0.8V, T
J
= 125°C
V
FB
= 0V
I
SW
= 1A
I
SW
= 1A
PV
IN
= 36V, V
SW
= 36V, V
EN
= 0V, V
BST
= 41V
PV
IN
= 36V, V
SW
= 0V, V
EN
= 0V, V
BST
= 41V
T
J
Rising
4.8
4
2
7
4.3
31
31
10
10
5.7
A
A
mΩ
mΩ
55
55
160
2
µA
µA
°C
°C
March 2012
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M9999-030912-A
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