MIC22705
1MHz, 7A Integrated Switch High-Efficiency
Synchronous Buck Regulator
General Description
The Micrel MIC22705 is a high-efficiency, 7A integrated
switch synchronous buck (step-down) regulator. The
MIC22705 is optimized for highest efficiency, achieving
more than 95% efficiency while still switching at 1MHz.
The ultra-high speed control loop keeps the output voltage
within regulation even under the extreme transient load
swings commonly found in FPGAs and low-voltage ASICs.
The output voltage is pre-bias safe and can be adjusted
down to 0.7V to address all low-voltage power needs.
The MIC22705 offers a full range of sequencing and
tracking options. The Enable/Delay (EN/DLY) pin,
combined with the Power Good (PG) pin, allows multiple
outputs to be sequenced in any way during turn-on and
turn-off. The Ramp Control™ (RC) pin allows the device to
be connected to another product in the MIC22xxx and/or
MIC68xxx family, to keep the output voltages within a
certain
∆V
on start-up.
The MIC22705 is available in a 24-pin 4mm x 4mm MLF
®
with a junction operating range from –40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at:
www.micrel.com.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Input voltage range: 2.9V to 5.5V
Output voltage adjustable down to 0.7V
Output load current up to 7A
Safe start-up into a pre-biased load
Full sequencing and tracking capability
Power Good output
Efficiency > 95% across a broad load range
Ultra-fast transient response
Easy RC compensation
100% maximum duty cycle
Fully-integrated MOSFET switches
Thermal-shutdown and current-limit protection
24-pin 4mm x 4mm MLF
®
–40°C to +125°C junction temperature range
Applications
•
•
•
•
•
High power density point-of-load conversion
Servers, routers, and base stations
DVD recorders / Blu-ray players
Computing peripherals
FPGAs, DSP and low voltage ASIC power
_________________________________________________________________________________________________________________________
Typical Application
Efficiency (V
IN
= 5.0V)
vs. Output Current
100
95
90
3.3V
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0
1
2
3
4
5
V
IN
= 5.0V
2.5V
6
7
OUTPUT CURRENT (A)
MIC22705 7A 1MHz Synchronous Output Converter
Ramp Control is a trademark 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
December 2010
M9999-121710-A
Micrel, Inc.
MIC22705
Ordering Information
Part Number
MIC22705YML
Note:
1. Other Voltage available. Contact Micrel for details.
Voltage
Adjustable
Junction Temperature Range
–40°C to +125°C
Package
24-Pin 4x4 MLF
®
Lead Finish
Pb-Free
Pin Configuration
24-Pin 4mm
×
4mm MLF
®
(ML)
Pin Description
Pin Number
1, 6, 13, 18
Pin Name
PVIN
Description
Power Supply Voltage (Input): The PVIN pins are the input supply to the internal P-Channel
Power MOSFET. A 22µF ceramic is recommended for bypassing at each PVIN pin. The SVIN
pin must be connected to a PVIN pin.
Enable/Delay (Input): This pin is internally fed with a 1µA current source from SVIN. A delayed
turn on is implemented by adding a capacitor to this pin. The delay is proportional to the
capacitor value. The internal circuits are held off until EN/DLY reaches the enable threshold of
1.24V. This pin is pulled low when the input voltage is lower than the UVLO threshold.
Delay (Input): Capacitor to ground sets internal delay timer. Timer delays Power Good (PG)
output at turn-on and ramp down at turn-off.
Ramp Control: A capacitor from the RC pin-to-ground determines slew rate of output voltage
during start-up. The RC pin is internally fed with a 1µA current source. The output voltage tracks
the RC pin voltage. The slew rate is proportional by the internal 1µA source and RC pin
capacitor. This feature can be used for tracking capability as well as soft start.
PG (Output): This is an open drain output that indicates when the output voltage is below 90% of
its nominal voltage. The PG flag is asserted without delay when the enable is set low or when the
output goes below the 90% threshold.
Feedback: Input to the error amplifier. The FB pin is regulated to 0.7V. A resistor divider
connecting the feedback to the output is used to adjust the desired output voltage.
2
EN/DLY
3
DELAY
4
RC
5
14
PG
FB
December 2010
2
M9999-121710-A
Micrel, Inc.
MIC22705
Pin Description (Continued)
Pin Number
Pin Name
Description
Compensation Pin (Input): The MIC22705 uses an internal compensation network containing a
fixed-frequency zero (phase lead response) and pole (phase lag response) which allows the
external compensation network to be much simplified for stability. The addition of a single
capacitor and resistor to the COMP pin will add the necessary pole and zero for voltage mode
loop stability using low-value, low-ESR ceramic capacitors.
Signal Ground: Internal signal ground for all low power circuits.
Signal Power Supply Voltage (Input): This pin is connected externally to the PVIN pin. A 2.2µF
ceramic capacitor from the SVIN pin to SGND must be placed next to the IC.
Power Ground: Internal ground connection to the source of the internal N-Channel MOSFETs.
Switch (Output): This is the connection to the drain of the internal P-Channel MOSFET and drain
of the N-Channel MOSFET. This is a high-frequency, high-power connection; therefore traces
should be kept as short and as wide as practical.
Exposed Pad (Power): Must be connected to the GND plane for full output power to be realized.
15
COMP
16
17
7, 12, 19, 24
8, 9, 10, 11,
20, 21, 22, 23
EP
SGND
SVIN
PGND
SW
GND
December 2010
3
M9999-121710-A
Micrel, Inc.
MIC22705
Absolute Maximum Ratings
(1, 2)
PV
IN
to PGND.................................................... –0.3V to 6V
SV
IN
to PGND..................................................–0.3V to PV
IN
V
SW
to PGND...................................................–0.3V to PV
IN
V
DELAY
to PGND...............................................–0.3V to PV
IN
V
EN/DLY
to PGND .............................................. -0.3V to PV
IN
V
PG
to PGND ...................................................–0.3V to PV
IN
Junction Temperature ................................................ 150°C
PGND to SGND ............................................. –0.3V to 0.3V
Storage Temperature Range ....................–65°C to +150°C
Lead Temperature (soldering, 10s)............................ 260°C
Operating Ratings
(3)
Supply Voltage (PV
IN
/SV
IN
) .............................. 2.9V to 5.5V
Power Good Voltage (V
PG
)...................................0V to PV
IN
Enable Input (V
EN/DLY
)...........................................0V to PV
IN
Junction Temperature (T
J
) ..................–40°C
≤
T
J
≤
+125°C
Package Thermal Resistance
4mm x 4mm MLF
®
-24 (θ
JC
)................................14°C/W
4mm x 4mm MLF
®
-24 (θ
JA
)................................40°C/W
Electrical Characteristics
(4)
SV
IN
= PV
IN
= V
EN/DLY
= 3.3V, V
OUT
= 1.8V, T
A
= 25°C, unless noted. Bold values indicate –40°C< T
J
< +125°C.
Parameter
Power Input Supply
Input Voltage Range (PV
IN
)
Undervoltage Lockout Trip Level
UVLO Hysteresis
Quiescent Supply Current
Shutdown Current
Reference
Feedback Reference Voltage
Load Regulation
Line Regulation
FB Bias Current
Enable Control
EN/DLY Threshold Voltage
EN Hysteresis
EN/DLY Bias Current
RC Ramp Control
RC Pin Source Current
Oscillator
Switching Frequency
Maximum Duty Cycle
Short Current Protection
Current Limit
Notes:
1.
2.
3.
4.
Exceeding the absolute maximum rating may damage the device.
Devices are ESD sensitive. Handling precautions recommended.
The device is not guaranteed to function outside its operating rating.
Specification for packaged product only.
Condition
Min.
2.9
2.55
Typ.
Max.
5.5
2.9
1.3
10
0.714
Units
V
V
mV
mA
µA
V
%
%
nA
V
mV
µA
µA
MHz
%
A
PV
IN
Rising
V
FB
= 0.9V (not switching)
V
EN/DLY
= 0V
2.75
420
0.85
5
0.7
0.2
0.2
10
1.24
10
1.0
1.0
1.0
0.686
I
OUT
= 100mA to 7A
V
IN
= 2.9V to 5.5V; I
OUT
= 100mA
V
FB
= 0.5V
1.14
V
EN/DLY
= 0.5V; V
IN
= 2.9V and V
IN
= 5.5V
V
RC
= 0.35V
0.7
0.7
0.8
100
7
1.34
1.3
1.3
1.2
V
FB
≤
0.5V
V
FB
= 0.5V
11
21
December 2010
4
M9999-121710-A
Micrel, Inc.
MIC22705
Electrical Characteristics
(4)
(Continued)
V
IN
= PV
IN
= V
EN/DLY
= 3.3V, V
OUT
= 1.8V, T
A
= 25°C, unless noted. Bold values indicate –40°C< T
J
< +125°C.
Parameter
Internal FETs
Top-MOSFET R
DS(ON)
Bottom-MOSFET R
DS(ON)
SW Leakage Current
V
IN
Leakage Current
Power Good (PG)
PG Threshold
Hysteresis
PG Output Low Voltage
PG Leakage Current
PG DELAY Pin Source Current
Thermal Protection
Over-temperature Shutdown
Over-temperature Shutdown
Hysteresis
I
PG
= 5mA (sinking), V
EN/DLY
= 0V
V
PG
= 5.5V; V
FB
= 0.9V
V
PG
= 0V; V
FB
= 0.9V
T
J
Rising
0.7
Threshold % of V
FB
from V
REF
−7.5
−10
2.0
144
1.0
1.0
160
20
2.0
1.3
−12.5
%
%
mV
μA
µA
°C
°C
Condition
V
FB
= 0.5V, I
SW
= 1A
V
FB
= 0.9V, I
SW
= -1A
PV
IN
= 5.5V, V
SW
= 5.5V, V
EN
= 0V
PV
IN
= 5.5V, V
SW
= 0V, V
EN
= 0V
Min.
Typ.
30
25
60
25
Max.
Units
mΩ
mΩ
µA
December 2010
5
M9999-121710-A
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