MIC24056
12V, 12A High-Efficiency Buck Regulator
SuperSwitcher II
General Description Features
HyperLight Load efficiency up to 80% at 10mA
The Micrel MIC24056 is a constant-frequency,
synchronous DC/DC buck regulator featuring adaptive on-
Hyper Speed Control architecture enables
time control architecture. The MIC24056 operates over a
High delta V operation (V = 19V and V = 0.8V)
IN OUT
supply range of 4.5V to 19V. It has an internal linear
Small output capacitance
regulator which provides a regulated 5V to power the
Input voltage range: 4.5V to 19V
internal control circuitry. MIC24056 operates at a constant
600kHz switching frequency in continuous-conduction
Output current up to 12A
mode and can be used to provide up to 12A of output
Up to 95% efficiency
current. The output voltage is adjustable down to 0.8V.
Adjustable output voltage from 0.8V to 5.5V
Micrels HyperLight Load architecture provides the same
1% FB accuracy
high efficiency and ultra-fast transient response as the
Any Capacitor stable zero-to-high ESR
Hyper Speed Control architecture under medium to
600kHz switching frequency
heavy loads, but also maintains high efficiency under light
load conditions by transitioning to variable frequency,
Power good (PG) output
discontinuous mode operation.
Foldback current-limit and hiccup mode short-circuit
The MIC24056 offers a full suite of protection features to
protection
ensure protection of the IC during fault conditions. These
Safe start-up into pre-biased loads
include undervoltage lockout to ensure proper operation
40C to +125C junction temperature range
under power-sag conditions, thermal shutdown, internal
Available in 28-pin 5mm 6mm QFN package
soft start to reduce the inrush current, foldback current-
limit and hiccup mode short-circuit protection. The
Applications
MIC24056 includes a power good (PG) output to allow
simple sequencing.
Servers, work stations
The 12A Hyper Speed Control part, MIC24055, is also
Routers, switches, and telecom equipment
available on Micrels web site.
Base stations
All support documentation can be found on Micrels web
site at: www.micrel.com.
___________________________________________________________________________________________________________
Typical Application
Efficiency (VIN = 12V)
vs. Output Current
100
95
5.0V
90 3.3V
2.5V
85
1.8V
1.5V
80
1.2V
1.0V
75
0.9V
0.8V
70
65
60
55
VIN = 12V
50
0 3 6 9 12 15
OUTPUT CURRENT (A)
HyperLight Load is a registered trademark of Micrel, Inc.
Hyper Speed Control, SuperSwitcher II, 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 Micrel, Inc. MIC24056
Ordering Information
Part Number Switching Frequency Voltage Package Junction Temperature Range Lead Finish
MIC24056YJL 600kHz Adjustable 28-Pin 5mm 6mm QFN 40 C to +125 C Pb-Free
Pin Configuration
28-Pin 5mm x 6mm QFN (JL)
(Top View)
Pin Description
Pin Number Pin Name Pin Function
5V Internal Linear Regulator Output. PVDD supply is the power MOSFET gate drive supply voltage
1 PVDD and created by internal LDO from VIN. When VIN < +5.5V, PVDD should be tied to PVIN pins. A
2.2F ceramic capacitor from the PVDD pin to PGND (Pin 2) must be place next to the IC.
Power Ground. PGND is the ground path for the MIC24056 buck converter power stage. The
PGND pins connect to the low-side N-Channel internal MOSFET gate drive supply ground, the
2, 5, 6,
PGND sources of the MOSFETs, the negative terminals of input capacitors, and the negative terminals of
7, 8, 21
output capacitors. The loop for the power ground should be as small as possible and separate from
the signal ground (SGND) loop.
3 NC No Connect.
Switch Node Output. Internal connection for the high-side MOSFET source and low-side MOSFET
4, 9,
SW drain. Due to the high-speed switching on this pin, the SW pin should be routed away from sensitive
10, 11, 12
nodes.
High-Side N-Internal MOSFET Drain Connection Input. The PVIN operating voltage range is from
13,14,15,
PVIN
4.5V to 19V. Input capacitors between the PVIN pins and the Power Ground (PGND) are required to
16,17,18,19
keep the connection short.
Boost Output. Bootstrapped voltage to the high-side N-channel MOSFET driver. A Schottky diode is
connected between the PVDD pin and the BST pin. A boost capacitor of 0.1F is connected between
20 BST
the BST pin and the SW pin. Adding a small resistor at the BST pin can slow down the turn-on time
of high-side N-Channel MOSFETs.
2
December 2012 M9999-121012-A