MIC24055
12V, 12A High-Efficiency Buck Regulator
SuperSwitcher II
General Description Features
Hyper Speed Control architecture enables
The Micrel MIC24055 is a constant-frequency,
synchronous buck regulator featuring a unique adaptive
- High delta V operation (V = 19V and V = 0.8V)
IN OUT
on-time control architecture. The MIC24055 operates over
- Small output capacitance
an input supply range of 4.5V to 19V and provides a
Input voltage range: 4.5V to 19V
regulated output of up to 12A of output current. The output
Output current up to 12A
voltage is adjustable down to 0.8V with a guaranteed
Up to 95% efficiency
accuracy of 1%, and the device operates at a switching
Adjustable output from 0.8V to 5.5V
frequency of 600kHz.
1% feedback accuracy
Micrels Hyper Speed Control architecture allows for
ultra-fast transient response while reducing the output Any Capacitor Stable zero-to-high ESR
capacitance and also makes (High V )/(Low V )
IN OUT
600kHz switching frequency
operation possible. This adaptive t ripple control
ON
No external compensation
architecture combines the advantages of fixed-frequency
Power good (PG) output
operation and fast transient response in a single device.
Foldback current-limit and hiccup mode short-circuit
The MIC24055 offers a full suite of protection features to
protection
ensure protection of the IC during fault conditions. These
Supports safe startup into a pre-biased load
include undervoltage lockout to ensure proper operation
40C to +125C junction temperature range
under power-sag conditions, internal soft-start to reduce
inrush current, foldback current limit, hiccup mode short-
Available in 28-pin 5mm 6mm QFN package
circuit protection and thermal shutdown. An open-drain
power good (PG) pin is provided.
Applications
The 12A HyperLight Load part, MIC24056, is also
available on Micrels web site.
Server and work stations
All support documentation can be found on Micrels web
Routers, switches and telecom equipment
site at: www.micrel.com.
Base station
___________________________________________________________________________________________________________
Typical Application
Efficiency (VIN = 12V)
vs. Output Current
100
95
5.0V
3.3V
90
2.5V
1.8V
85
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. MIC24055
Ordering Information
Junction Temperature
Part Number Switching Frequency Voltage Package Lead Finish
Range
MIC24055YJL 600kHz Adjustable 28-Pin 5mm 6mm QFN 40 C to +125 C Pb-Free
Pin Configuration
28-Pin 5mm 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 MIC24055 buck converter power stage. The
PGND pins connect to the low-side N-Channel internal MOSFET gate drive supply ground, the
2, 5, 6, 7, 8,
PGND sources of the MOSFETs, the negative terminals of input capacitors, and the negative terminals of
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, 10,
SW drain. Due to the high-speed switching on this pin, the SW pin should be routed away from sensitive
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.
M9999-120712-A
December 2012 2