AX6614 (Preliminary)
2A Ultra Low Dropout Linear Regulator
GENERAL DESCRIPTION
The AX6614 is a 2A ultra low dropout linear regulator. This product is specifically
designed to provide well supply voltage for front-side-bus termination on motherboards
and NB applications. The IC needs two supply voltages, a control voltage for the
circuitry and a main supply voltage for power conversion, to reduce power dissipation
and provide extremely low dropout. The AX6614 integrates many functions. A
Power-On-Reset (POR) circuit monitors both supply voltages to prevent wrong
operations. A thermal shutdown and current limit functions protect the device against
thermal and current over-loads. A POK indicates the output status with time delay
which is set internally. It can control other converter for power sequence. The AX6614
can be enabled by other power system. Pulling and holding the EN pin below 0.3V
shuts off the output.
The AX6614 is available in SOP8-EP package which features small size as
SOP-8 and an Exposed Pad to reduce the junction-to-case resistance, being applicable
in 2~3W applications.
FEATURES
- Ultra Low Dropout - 0.22V(typical) at 2A Output Current
- Low ESR Output Capacitor (Multi-layer Chip Capacitors (MLCC)) Applicable
- 0.8V Reference Voltage
- Fast Transient Response
- Adjustable Output Voltage by External Resistors
- Power-On-Reset Monitoring on Both VCNTL and VIN Pins
- Internal Soft-Start
- Under-Voltage Protection
- Current-Limit and Thermal Shutdown Protection
- Power-OK Output with a Delay Time
- SOP-8 with Exposed Pad Pb-Free Package.
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Rev.0.1 Apr.24, 2008
AX6614 (Preliminary)
Block Diagram
N-MOSFET
VIN VOUT
Current
Limit Error
VCNTL Power -ON Amp
Reset - +
Soft-Start
And
Control Logic Bandgap
EN Enable
UV
Thermal + -
Shutdown FB
0.4V
+
GND Delay POK
-
90%
Vref
POK
PIN ASSIGNMENT
The package of AX6614 is SOP-8L-EP; the pin assignment is given by:
Name Description
GND GND pin
( Top View )
FB Feedback pin
POK 1 8 GND VOUT IC power supply pin
EN 2 7 FB
Internal Pull High.
AX5913
GND EN EN=high or Floating Æ Enable
VIN 3 6 VOUT EN=Low Æ Shutdown mode
VCNTL 4 5 NC POK Power OK Output Pin
VCNTL CNTL Pin Input Voltage
SOP-8L-EP
VIN Input Voltage
NC No connect
ORDER/MARKING INFORMATION
Order Information Top Marking
AX6614 X X X
AX 6614 Part number
XXXXX ID code: internal
VOUT Package Type Packing
WW: 01~52
A : ADJ ES: EP-SOP-8L Blank : Tube
A : Taping Year: 07 = 2007
2/9
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Rev.0.1 Apr.24, 2008
AX6614 (Preliminary)
Absolute Maximum Ratings (at Ta=25℃)
Characteristics Symbol Rating Unit
VCNTL Supply Voltage VCNTL -0.3 to 7 V
VIN Supply Voltage VIN -0.3 to 3.3 V
EN and FB Pin Voltage VI/O -0.3 to VCNTL+0.3 V
Power good Voltage VPOK -0.3 to 7 V
Power Dissipation PD 3 W
Storage Temperature Range TST -65 to +150 ℃
Junction Temperature Range TJ -40 to 125 ℃
Operating Temperature Range TOP -40 to +85 ℃
Thermal Resistance from Junction to case θJC 15 ℃/W
Thermal Resistance from Junction to ambient θJA 40 ℃/W
Note: θJA is measured with the PCB copper area (need connect to Expose-Pad) of
approximately 1.5 in2 (Multi-layer)
Recommended Operating Conditions
Characteristics Symbol Conditions Rating Unit
VCNTL Supply Voltage VCNTL 4.5 to 6 V
VIN Supply Voltage VIN 1.1 to 3.3 V
Output Voltage VOUT VCNTL=5V 0.8 to 2.8 V
Output Current IOUT 0 to 2 A
Electrical Characteristics
(VCNTL = 5V, VIN = 1.5V, VOUT = 1.2V, TA=25℃ unless otherwise specified)
Characteristics Symbol Conditions Min Typ Max Units
VCNTL POR Threshold VCNTL 2.7 2.9 3.1 V
VCNTL POR Hysteresis VCNTL(hys) - 0.4 - V
VIN POR Threshold VIN 0.8 0.9 1.0 V
VIN POR Hysteresis VIN(hys) - 0.5 - V
VCNTL Nominal Supply
ICNTL EN= VCNTL 0.4 1 2 mA
Current
VCNTL Shuntdown Current ISD EN= 0V - 18 30 uA
Feedback Voltage VFB VCNTL=4.5 ~ 6V 0.784 0.8 0.816 V
Load Regulation IOUT=0A ~ 2A - 0.06 0.25 %
Dropout Voltage VDROP IOUT = 2A, VCNTL=5V - 0.22 0.3 V
VOUT<2V,IOUT=2A - 110 -
Internal MOSFET RDS-ON RDS-ON mΩ
2V<VOUT <2.8V,IOUT=2A - 160 -
3/9
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Rev.0.1 Apr.24, 2008
AX6614 (Preliminary)
Electrical Characteristics (Cont.)
VOUT Pull Low Resistance EN=0V - 90 120 Ω
Soft Start Time TSS - 1 - mS
EN Pin Logic High VENH Enable 1.2 - -
V
threshold voltage VENL Disable - - 0.4
EN Hysteresis - 30 - mV
EN Pin Pull-Up Current IEN EN=GND - 10 - uA
VCNTL=4.5~6V,
Current Limit ILIM TJ= -40 ~ 125℃ 2.3 - - A
Ripple VIN - 65 -
PSRR F=120Hz, IOUT=100mA dB
Rejection VCNTL - 65 -
Under-Voltage Threshold VFB Falling - 0.4 - V
POK Threshold Voltage for
VPOK VFB Rising 89% 92% 95% VFB
Power OK
POK Threshold Voltage for
VPNOK VFB Falling 78% 81% 84% VFB
Power Not OK
POK Low Voltage POK sinks 5mA - 0.25 0.4 V
POK Delay Time TDELAY 0.8 2 10 mS
Thermal shutdown Temp TSD - 150 - ℃
Thermal Shutdown
- 50 - ℃
Hysteresis
4/9
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Rev.0.1 Apr.24, 2008
AX6614 (Preliminary)
Application Circuit
1. Using an Output Capacitor with ESR≧20mΩ
R3
1K
U1
VCNTL=5V
4 3 VIN=1.5V
VCNTL VIN
C2 C3
5
1 NC 100uF 0.1uF
ON POK 6
2 VOUT
EN
C1
OFF 8 7
GND FB
Vout=1.2V/2A
1uF
AX6614
R1 C6
1K
12~48nF
C4 C5
220uF 0.1u
R2
2K
2. Using an MLCC as the Output Capacitor
R3
1K
U2
VCNTL=5V
4 3 VIN=1.5V
VCNTL VIN
C3
5
1 NC 22uF
ON POK 6
2 VOUT
EN
OFF 8 7
C1 GND FB Vout=1.2V/2A
1uF
AX6614 R1 C6 C5
39K
56pF 22u
R2
78K
VOUT=VFB*(1+R1/R2)
VFB = 0.8V
5/9
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AX6614 (Preliminary)
Function Pin Descriptions
FB
Connecting this pin to an external resistor divider receives the feedback voltage
of the regulator. The output voltage set by the resistor divider is determined by:
Where R1 is connected from VOUT to FB with Kelvin sensing and R2 is
connected from FB to GND. A bypass capacitor may be connected with R1in parallel to
improve load transient response. The recommended R2 and R1 are in the range of
100~10kW.
VIN
Main supply input pins for power conversions. The voltage at this pin is
monitored for Power-On Reset purpose.
VCNTL
Power input pin of the control circuitry. Connecting this pin to a +5V
(recommended) supply voltage provides the bias for the control circuitry. The voltage at
this pin is monitored for Power-On Reset purpose.
POK
Power-OK signal output pin. This pin is an open-drain output used to indicate
status of output voltage by sensing FB voltage. This pin is pulled low when the rising FB
voltage is not above the VPOK threshold or the falling FB voltage is below the VPOK
threshold, indicating the output is not OK.
EN
Enable control pin. Pulling and holding this pin below 0.3V shuts down the output.
When re-enabled, the IC undergoes a new soft-start cycle. Left this pin open, an
internal current source 10mA pulls this pin up to VCNTL voltage, enabling the regulator.
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Rev.0.1 Apr.24, 2008
AX6614 (Preliminary)
VOUT
Output of the regulator. Please connect Pin 6 using wide tracks. It is necessary
to connect an output capacitor with this pin for closed-loop compensation and improving
transient responses.
Function Descriptions
Power-On-Reset
A Power-On-Reset (POR) circuit monitors both input voltages at VCNTL and VIN
pins to prevent wrong logic controls. The POR function initiates a soft-start process
after the two supply voltages exceed their rising POR threshold voltages during
powering on. The POR function also pulls low the POK pin regardless the output
voltage when the VCNTL voltage falls below its falling POR threshold.
Internal Soft-Start
An internal soft-start function controls rise rate of the output voltage to limit the
current surge at start-up. The typical soft-start interval is about 1mS.
Output Voltage Regulation
An error amplifier working with a temperature compensated 0.8V reference and
an output NMOS regulates output to the preset voltage. The error amplifier designed
with high bandwidth and DC gain provides very fast transient response and less load
regulation. It compares the reference with the feedback voltage and amplifies the
difference to drive the output NMOS which provides load current from VIN to VOUT.
Current-Limit
The AX6614 monitors the current via the output NMOS and limits the maximum
current to prevent load and AX6614 from damages during overload or short circuit
conditions.
Under-Voltage Protection (UVP)
The AX6614 monitors the voltage on FB pin after soft-start process is finished.
Therefore the UVP is disabling during soft-start. When the voltage on FB pin falls below
the under-voltage threshold, the UVP circuit shuts off the output immediately. After a
while, the AX6614 starts a new soft-start to regulate output.
7/9
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AX6614 (Preliminary)
Thermal Shutdown
A thermal shutdown circuit limits the junction temperature of AX6614. When the
junction temperature exceeds +150°C, a thermal sensor turns off the output NMOS,
allowing the device to cool down. The regulator regulates the output again through
initiation of a new soft-start cycle after the junction temperature cools by 50°C, resulting
in a pulsed output during continuous thermal overload conditions. The thermal
shutdown designed
8/9
Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.0.1 Apr.24, 2008
AX6614 (Preliminary)
Package Outlines
H
Expose Pad
E
Y
L
DETAIL A
D
7 (4X)
A2
C
A1
e
y DETAIL A
Dimensions In Millimeters Dimensions In Inches
Symbol
Min. Nom. Max. Min. Nom. Max.
A 1.40 1.60 1.75 0.055 0.063 0.069
A1 0.10 - 0.25 0.040 - 0.100
A2 1.30 1.45 1.50 0.051 0.057 0.059
C 0.19 0.20 0.25 0.0075 0.008 0.010
D 4.80 4.90 5.00 0.189 0.193 0.197
E 3.80 3.90 4.00 0.150 0.154 0.157
H 5.79 5.99 6.20 0.228 0.236 0.244
L 0.38 0.71 1.27 0.015 0.028 0.050
b 0.33 0.41 0.51 0.013 0.016 0.020
e 1.27 TYP 0.050 TYP
y - - 0.10 - - 0.004
X - 2.34 - - 0.092 -
Y - 2.34 - - 0.092 -
θ 0O - 8O 0O - 8O
9/9
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Rev.0.1 Apr.24, 2008
