MIC68400
4A Sequencing LDO with Tracking and
Ramp Control™
General Description
The MIC68400 is a high peak current LDO regulator
designed specifically for powering applications such as
FPGA core voltages that require high start up current with
lower nominal operating current. Capable of sourcing 4A of
current for start-up, the MIC68400 provides high power
from a small MLF
®
leadless package. The MIC68400 can
also implement a variety of power-up and power-down
protocols such as sequencing, tracking, and ratiometric
tracking.
The MIC68400 operates from a wide input range of 1.65V
to 5.5V, which includes all of the main supply voltages
commonly available today. It is designed to drive digital
circuits requiring low voltage at high currents (i.e. PLDs,
DSP, microcontroller, etc.). The MIC68400 incorporates a
delay pin (Delay) for control of power on reset output
(POR) at turn-on and power-down delay at turn-off. In
addition there is a ramp control pin (RC) for either tracking
applications or output voltage slew rate adjustment at turn-
on and turn-off. This is important in applications where the
load is highly capacitive and in-rush currents can cause
supply voltages to fail and microprocessors or other
complex logic chips to hang up.
Multiple MIC68400s can be daisy chained in two modes.
In tracking mode the output voltage of the Master drives
the RC pin of a Slave so that the Slave tracks the main
regulator during turn-on and turn-off. In sequencing mode
the POR of the Master drives the enable (EN) of the Slave
so that it turns on after the Master and turns off before (or
after) the Master. This behavior is critical for power-up and
power-down control in multi-output power supplies. The
MIC68400 is fully protected offering both thermal, current
limit protection, and reverse current protection.
The MIC68400 has a junction temperature range of
–40°C to +125°C and is available in fixed as well as an
adjustable option. The MIC68400 is offered in the tiny
®
16-pin 4mm x 4mm MLF package.
Features
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Stable with 10µF ceramic capacitor
Input voltage range: 1.65V to 5.5V
0.5V reference
±2.0% output tolerance over temperature
4A maximum output current – peak start up
3A continuous operating current
Tracking on turn-on and turn-off with pin strapping
Timing controlled sequencing on/off
Programmable Ramp Control™ for in-rush current
limiting and slew rate control of the output voltage
during turn-on and turn-off
Power-on reset (POR) supervisor with programmable
delay time
Single master can control multiple slave regulators
with tracking output voltages
Tiny 4mm x 4mm MLF
®
package
Maximum dropout (V
IN
– V
OUT
) of 500mV over
temperature at 3A output current
Fixed and adjustable output voltages
Excellent line and load regulation specifications
Logic controlled shutdown
Thermal shutdown and current limit protection
Applications
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FPGA/PLD power supply
Networking/telecom equipment
Microprocessor core voltage
High efficiency linear post regulator
Sequenced or tracked power supply
Ramp Control is a trademark of Micrel, Inc.
MLF and
MicroLeadFrame
is a registered trademark 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
August 2009
M9999-081809-C
Micrel, Inc.
MIC68400
Pin Configuration
®
16-Pin 4mm × 4mm MLF (ML)
Fixed Voltages
16-Pin 4mm × 4mm MLF
®
(ML)
Adjustable Voltages
Pin Description
(Pin Numbering may change depending on layout considerations)
Pin Number
MIC68400YML
1, 2, 15, 16
3
4
5
6, 14
7, 8, Tab
9
Pin Name
VIN
Delay
RC
EN
NC
GND
POR
Pin Function
Input: Input voltage supply pin. Place a capacitor to ground to bypass the
input supply.
Delay: Capacitor to ground sets internal delay timer. Timer delays power-on
reset (POR) output at turn-on, and ramp down at turn-off.
Ramp Control: May be voltage driven for tracking applications or a capacitor
to ground will set the slew rate of output voltage during start-up.
Enable (Input): CMOS compatible input. Logic high = enable, logic low =
shutdown.
Not internally connected.
Ground.
Power-on Reset: Open-drain output device indicates when the output is in
regulation. High (open) means device is regulating within 10%. POR onset
can be delayed using a single capacitor from Delay to ground.
Output Voltage Sense Pin: Connect directly to output pin.
Adjustable regulators: Feedback input. Connect to resistor voltage divider.
Output Voltage: Output of voltage regulator. Place capacitor to ground to
bypass the output voltage. Minimum load current is 100µA. Nominal bypass
capacitor is 10µF.
10 (Fixed)
10 (ADJ)
11, 12, 13
SNS
ADJ
VOUT
August 2009
5
M9999-081809-C
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