AAT2688 Datasheet PDF - Advanced Analogic Technologies

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AAT2688
Advanced Analogic Technologies

Part Number AAT2688
Description 4.5A PMIC Solution
Page 20 Pages


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PRODUCT DATASHEET
AAT2688
SystemPowerTM 4.5A PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters
General Description
The AAT2688 provides two independently regulated DC
outputs: a high voltage synchronous step-down (Buck)
regulator and a low input voltage step-down low dropout
(LDO) regulator. The PMIC is optimized for low cost 12V
adapter inputs, making the device the ideal system-on-
a-chip power solution for consumer communications
equipment.
Channel 1 is a step-down regulator with an input voltage
range of 6.0V to 24V, providing up to 4.5A output cur-
rent. 490kHz fixed switching frequency allows small L/C
filtering components. Channel 1 utilizes voltage mode
control configured for optimum performance across the
entire output voltage and load range.
Channel 2 is a low-dropout (LDO) regulator providing up
to 600mA output current. The device provides low out-
put noise, low quiescent current, and excellent transient
response.
The step-down regulator includes integrated over-cur-
rent, soft-start and over-temperature protection. Inde-
pendent input and enable pins provide maximum design
flexibility.
The AAT2688 is available in the Pb-free 4mm x 5mm
24-pin TQFN package. The rated operating temperature
range is -40°C to 85°C.
Features
• 2-Output Step-Down Converters:
Channel 1 (Buck): VIN1 = 6.0 to 24.0V
VOUT1 Adjustable from 0.8V to 5.5V
IOUT1 up to 4.5A
High Switching Frequency
Voltage Mode Control
High Accuracy ±1.5%
PWM Fixed Frequency for Low Ripple
Channel 2 (LDO): VIN2 = 2.7V to 5.5V
IOUT2 up to 600mA
1V Dropout Voltage at 600mA IOUT
• Small Solution Size
• System on a Chip
• Ultra-small External L/C
• Shutdown Current <35μA
• Independent Enable Pins
• Over-Current and Over-Temperature Protection
• Internal Soft Start
• 4x5mm 24-Pin TQFN Low Profile Package
• -40°C to 85°C Temperature Range
Applications
• DSL and Cable Modems
• Notebook Computers
• Satellite Set-top Boxes
• Wireless LAN Systems
Typical Application
C3
0.1μF
D1
BAS16
J1 2
1
VIN1
6.0V -24.0V
C14
2.2μF
+ C1
220μF
25V
VIN2
C13
1μF
25V
C2
2.2μF
L1 4.7μH/5.3A
LX1
BST1 DL
VL1 RS1
OS1
IN1 FB1
Q1 C10
R2 C4
2.2nF
2K 220nF
R5
150
COMP1
AAT2688
R1
3.92k
C5
2.2nF
EN1
IN2 OUT2
C6
150pF
VOUT2
EN2 GND
C12
2.2μF
TQFN45-24
VOUT1
3.3V/4.5A
R3
9.09k
C7 C8
22μF 22μF
C9
22μF
R4
1.96k
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PRODUCT DATASHEET
AAT2688
SystemPowerTM 4.5A PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters
Pin Descriptions
Pin #
1, 2, 23, 24
3, 4, 9, 12
5
6
7
8
10
11
13
14
15
16
17
18, 19
20
21
22
EP
Symbol
LX1
N/C
BST1
EN1
GND2
EN2
IN2
OUT2
RS1
OS1
COMP1
FB1
GND1
VL1
DL1
PGND
IN1
EP
Function
Channel 1 step-down (Buck) converter switching pin. Connect output inductor to this pin. Connect both
LX1 pins together.
No connect. For optional routing reasons, pins 3 and 4 can be connected to VIN, pin 9 to pin 10 (IN2),
and pin 12 to pin 11 (OUT2).
Channel 1 step-down regulator boost drive input pin. Connect the cathode of fast rectier from this pin
and connect a 100nF capacitor from this pin to the channel 1 switching node (LX1) for internal hi-side
MOSFET gate drive.
Channel 1 step-down regulator enable input pin. Active high enables internal linear regulator and chan-
nel 1 output.
Ground pin for Channel 2. Power return pin for channel 2. Connect return of channel 2 input and output
capacitors close to this pin for best noise performance.
Channel 2 low dropout (LDO) enable input pin. Active high.
Input supply voltage pin for channel 2 linear low dropout (LDO) regulator. Connect 2.2μF ceramic input
capacitor close to this pin.
Output of channel 2 of linear low dropout (LDO) regulator. Connect a 2.2μF ceramic capacitor from this
pin to GND pin.
Channel 1 output current sense pin. Connect a small signal resistor from this pin to switching node
(LX1) to enable over-current sense for step-down converter. The current limit threshold varies with
sense resistor sizing.
Channel 1 output sense voltage pin. Connect to the output capacitor to enable over-current sense for
step-down converter.
Compensation pin for channel 1 step-down regulator. Connect a series resistor, capacitor network to
compensate the voltage mode control loop.
Feedback input pin for channel 1 step-down converter. Connect an external resistor divider to this pin to
program the output voltage to the desired value.
Ground pin for channel 1. Power return pin for channel 1. Connect return of channel 1 input and output
capacitors close to this pin for best noise performance.
Internal linear regulator. Connect a 2.2μF capacitor from this pin to GND pin.
Channel 1 gate drive for low side MOSFET. Connect to the gate pin of an external N type MOSFET (see
the "MOSFET Selection" section of this product datasheet).
Ground pin for both channels. Power return pin for both channels. Connect returns of both channels’
input and output capacitors close to this pin for best noise performance.
Input supply voltage pin for channel 1 step-down regulator. Connect both IN1 pins together. Connect
the input capacitor close to this pin for best noise performance.
Exposed Paddle. Tie to IN1. Connect to PCB heatsink for optimum thermal performance.
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PRODUCT DATASHEET
AAT2688
SystemPowerTM 4.5A PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters
Pin Configuration
TQFN45-24
(Top View)
LX1 1
LX1 2
N/C 3
N/C 4
BST1 5
EN1 6
GND2 7
19 VL1
18 VL1
17 GND1
EP 16 FB1
15 COMP1
14 OS1
13 RS1
Absolute Maximum Ratings1
Symbol
VIN(HI)
VIN(LO)
VBST1-LX1
VCONTROL
VEN2
TJ
TLEAD
Description
IN1, EN1, LX1 to GND
IN2, VL1 to GND
BST1 to LX1
FB1, COMP1, RS1, OS1, OUT2, DL1 to GND
EN2 to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Thermal Information
Symbol
PD
ΘJA
Description
Maximum Power Dissipation2
Thermal Resistance3
Value
-0.3 to 30.0
-0.3 to 6.0
-0.3 to 6.0
-0.3 to VIN(LO) + 0.3
-0.3 to VIN2 + 0.3
-40 to 150
300
Units
V
V
V
V
V
°C
°C
Value
3.0
33
Units
W
°C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board with exposed paddle connected to ground plane.
3. Derate 30mW/°C above 25°C ambient temperature.
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PRODUCT DATASHEET
AAT2688
SystemPowerTM 4.5A PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters
Electrical Characteristics1
VIN1 = 12.0V, VIN2 =3.3V; TA = -40°C to 85°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol Description
Conditions
Channel 1: 4.5A Step-Down (Buck) Converter
VIN1 Input Voltage
VIN1 Rising
VUVLO1
UVLO Threshold
VIN1 Hysteresis
VIN1 Falling
VOUT1
Output Voltage Range
VFB1 Feedback Pin Voltage
VOUT
Output Voltage Accuracy
IOUT1 = 0 to 4.5A
(ΔVOUT/VOUT)/
ΔVIN
Line Regulation
VIN1 = 6V to 24V, VOUT1 = 3.3V, IOUT1 = 4.5A
(ΔVOUT/VOUT)/
ΔIOUT
Load Regulation
VIN1 = 12V, VOUT1 = 3.3V, IOUT1 = 0A to 4.5A
IQ1 Quiescent Current
VEN1 = Low, No load, VFB1 = 1.2V
ISHDN1
Shutdown Current
VEN1 = High, VL1 = 0V
VOCP1
Over-Current Offset Voltage
VEN1 = Low, VIN1 = 6.0V to 24.0V, TA = 25°C
ILX1 LX1 Pin Leakage Current
VIN1 = 24.0V, VEN1 = 5.0V
DMAX
Maximum Duty Cycle
RDL1
Low Side Drive Source Resistance Pull-Up, VL1 = 4.5V
Pull-Down, VL1 = 4.5V
RDSON(H)
Hi Side On-Resistance
VL1 = 4.5V
FOSC1
Oscillator Frequency
FFOLDBACK1 Short Circuit Foldback Frequency Current Limit Triggered
tS1 Start-Up Time
From Enable Channel 1 to Output Regulation
Channel 2: 600mA Low Dropout (LDO) Regulator
VIN2
VDO2
IQ2
ISHDN2
Input Voltage
Dropout Voltage
Quiescent (Ground) Current
Shutdown Current
VOUT2(TOL)
Output Voltage Tolerance
eN Output Noise
98% · VOUT2(NOM), IOUT2 = 600mA
No load
VEN2 = GND
IOUT2= 1mA to 600mA, VIN2 = 2.7 to 5.5V,
TA = 25°C
IOUT2= 1mA to 600mA, VIN2 = 2.7 to 5.5V,
TA = -40°C to 85°C
BW = 300Hz to 50kHz
1kHz
PSRR
Power Supply Rejection Ratio
IOUT2 = 10mA
10kHz
1MHz
ILIMIT2
Current Limit
tS2 Enable Start-Up Delay
Over-Temperature, EN Logic
From Enable Channel 2 to Output Regulation
TSD1,2
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
VEN1,EN2(L)
VEN1(H)
VEN2(H)
IEN1,EN2
Enable Threshold Low
Enable Threshold High
Input Low Current
Min
6.0
3.0
0.8
0.576
-3.0
80
-1.0
350
2.7
-2.0
-3.5
700
2.5
1.4
-1.0
Typ
300
0.585
0.05
0.2
600
100
85
5.0
1.7
35
490
100
2.5
1000
70
250
67
47
45
800
15
135
15
Max
24.0
5.0
5.5
0.594
+3.0
35
120
1.0
650
5.5
1300
125
1.0
+2.0
+3.5
0.6
1.0
Units
V
V
mV
V
V
V
%
%/V
%/A
μA
μA
mV
μA
%
Ω
mΩ
kHz
kHz
ms
V
mV
μA
μA
%
%
μVRMS
dB
mA
μs
°C
°C
V
V
μA
1. The AAT2688 is guaranteed to meet performance specifications over the –40°C to +85°C operating temperature range and is assured by design, characterization and correla-
tion with statistical process controls.
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