Alpha & Omega AOZ1237QI-02 Schematic [ru]

AOZ1237QI-02

24V/8A Synchronous EZBuckTM Regulator

General Description

The AOZ1237 is a high-efficiency, easy-to-use DC/DC
synchronous buck regulator that operates up to 24V.
The device is capable of supplying 8A of continuous
output current with an output voltage adjustable down to

0.8V (±1.0%).

A proprietary constant on-time PWM control with input
feed-forward results in ultra-fast transient response while
maintaining relatively constant switching frequency over
the entire input voltage range. The switching frequency
can be externally programmed up to 1MHz.

The device features multiple protection functions such as
V

under-voltage lockout, cycle-by-cycle current limit,

CC

output over-voltage protection, short-circuit protection, as
well as thermal shutdown.

The AOZ1237 is available in a 4mm x 4mm QFN-23L
package and is rated over a -40°C to +85°C ambient
temperature range.

Features



Wide input voltage range

– 2.7V to 24V



8A continuous output current



Output voltage adjustable down to 0.8V (±1.0%)



Low R

– 35m high-side
– 8m low-side SRFET™



Constant On-Time with input feed-forward



Programmable frequency up to 1MHz



Selectable PFM light load operation



Ceramic capacitor stable



Adjustable soft start



Power Good output



Integrated bootstrap diode



Cycle-by-cycle current limit



Short-circuit protection



Over voltage protection



Thermal shutdown



Thermally enhanced 4mm x 4mm QFN-23L package

internal NFETs

DS(ON)

Applications



Portable computers



Compact desktop PCs



Servers



Graphics cards



Set-top boxes



LCD TVs



Cable modems



Point-of-load DC/DC converters



Telecom/Networking/Datacom equipment

Rev. 2.0 April 2013

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Typical Application

5V

Power Good

Off On

R3
100kΩ

R

TON

C4
1μF

C

SS

TON IN

VCC

AOZ1237

PGOOD

EN

PFM

SS

Power Ground

Analog Ground

BST

LX

FB

AGND

PGND

C5

0.1μF

L1

1μH

R1

2.65kΩ
1%

R2

8.06kΩ
1%

C2
33μF

AOZ1237QI-02

Input

2.7V to 24V

Output

1.05V, 8A

C3
44μF

Ordering Information

Part Number Ambient Temperature Range Package Environmental

AOZ1237QI-02 -40°C to +85°C 23-Pin 4mm x 4mm QFN Green Product

AOS Green Products use reduced levels of Halogens, and are also RoHS compliant.
Please visit www.aosmd.com/media/AOSGreenPolicy.pdf for additional information.

Pin Configuration

SS

IN

VCC

BST

PGND

LX

23 21 20 19 18

22

PGOOD

EN

PFM

AGND

FB

TON

1

2

3

IN

4

5

6

789 1110

IN

NC

IN

LX

LX

LX

LX

17

LX

16

PGND

15

PGND

14

PGND

13

PGND

12

Rev. 2.0 April 2013

23-Pin 4mm x 4mm QFN

(Top View)

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Page 2 of 15

Pin Description

Pin Number Pin Name Pin Function

Power Good Signal Output. PGOOD is an open-drain output used to indicate the status

1 PGOOD

2EN

3PFM

4 AGND Analog Ground.

5FB

6 TON On-Time Setting Input. Connect a resistor between VIN and TON to set the on time.

7 NC Not Connected. Connect to IN pins (8 and 9) to help with heat dissipation.

8, 9, 22 IN Supply Input. IN is the regulator input. All IN pins must be connected together.

12, 13, 14, 15, 19 PGND Power Ground.

10, 11, 16, 17, 18 LX Switching Node.

20 BST

21 VCC

23 SS

of the output voltage. It is internally pulled low when the output voltage is 10% lower than
the nominal regulation voltage for 50µs (typical time) or 15% higher than the nominal
regulation voltage. PGOOD is pulled low during soft-start and shut down.

Enable Input. The AOZ1237 is enabled when EN is pulled high. The device shuts down
when EN is pulled low.

PFM Selection Input. Connect PFM pin to VCC/VIN for forced PWM operation. Connect
PFM pin to ground for PFM operation to improve light load efficiency.

Feedback Input. Adjust the output voltage with a resistive voltage-divider between the
regulator’s output and AGND.

Bootstrap Capacitor Connection. The AOZ1237 includes an internal bootstrap diode.
Connect an external capacitor between BST and LX as shown in the Typical Application
diagram.

Supply Input for analog functions. Bypass VCC to AGND with a 1µF ceramic capacitor.
Place the capacitor close to VCC pin.

Soft-Start Time Setting Pin. Connect a capacitor between SS and AGND to set the
soft-start time.

AOZ1237QI-02

Rev. 2.0 April 2013

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AOZ1237QI-02

Absolute Maximum Ratings

Exceeding the Absolute Maximum Ratings may damage the
device.

Parameter Rating

IN, TON to AGND -0.3V to 30V

LX to AGND -2V to 30V

BST to AGND -0.3V to 36V

SS, PGOOD, FB, EN, VCC, PFM to
AGND

PGND to AGND -0.3V to +0.3V

Junction Temperature (T

Storage Temperature (T

ESD Rating

Note:

1. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5k

2. LX to PGND Transient (t<20ns) ------ -7V to V

(1)

) +150°C

J

) -65°C to +150°C

S



in series with 100pF.

IN

+ 7V.

-0.3V to 6V

2kV

Electrical Characteristics

TA = 25°C, V

-40°C to +85°C.

= 12V, V

IN

= 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of

CC

Maximum Operating Ratings

The device is not guaranteed to operate beyond the
Maximum Operating ratings.

Parameter Rating

Supply Voltage (VIN)2.7V

Output Voltage Range 0.8V to 0.85*V

Ambient Temperature (TA) -40°C to +85°C

Package Thermal Resistance

)40°C/W

(θ

JA

) 4.5°C/W

(θ

JC

Note:

3. Connect V

to external 5V for VIN = 2.7V ~ 6.5V application.

CC

(3)

to 24V

IN

Symbol Parameter Conditions Min. Typ. Max Units

V

IN

V

UVLO

I

q

I

OFF

V

FB

I

FB

Enable

V

EN

V

EN_HYS

PFM Control

V

PFM

V

PFMHYS

Modulator

T

ON

T

ON_MIN

T

OFF_MIN

IN Supply Voltage 2.7 24 V

Under-Voltage Lockout Threshold of VCC

Quiescent Supply Current of VCC I

Shutdown Supply Current V

Feedback Voltage

rising

V

CC

falling 3.2

V

CC

= 0, VFB = 1V, V

OUT

= 0V 120A

EN

T

= 25°C

A

TA = 0°C to 85°C

> 2V 11.5mA

EN

0.792

0.788

4.0

3.7

0.800

0.800

4.4

0.808

0.812

V

V

Load Regulation 0.5 %

Line Regulation 1%

FB Input Bias Current 200 nA

EN Input Threshold

Off threshold
On threshold 2.5

0.5
V

EN Input Hysteresis 100 mV

PFM Input Threshold

PFM Mode threshold
Force PWM threshold 2.5

0.5
V

PFM Input Hysteresis 100 mV

On Time

R

= 100k, VIN = 12V

TON

= 100k, VIN = 24V

R

TON

200 250

150

300

ns

Minimum On Time 100 ns

Minimum Off Time 250 400 ns

Rev. 2.0 April 2013

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Page 4 of 15

AOZ1237QI-02

Electrical Characteristics

TA = 25°C, V

= 12V, V

IN

= 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of

CC

(Continued)

-40°C to +85°C.

Symbol Parameter Conditions Min. Typ. Max Units

Soft-Start

I

SS_OUT

Power Good Signal

V

PG_LOW

V

PGH

V

PGL

T

PG_L

Under Voltage and Over Voltage Protection

V

PL

T

PL

V

PH

T

UV_LX

Power Stage Output

R

DS(ON)

R

DS(ON)

Over-current and Thermal Protection

I

LIM

SS Source Current VSS = 0

C

= 0.001F to 0.1F

SS

PGOOD Low Voltage I

= 1mA 0.5 V

OL

71015A

PGOOD Leakage Current ±1 A

PGOOD Threshold
(Low level to High level)

PGOOD Threshold
(High level to Low level)

FB rising (AOZ1237-02)
FB rising (AOZ1237-04)
FB falling (AOZ1237-04 only)

FB rising (AOZ1237-02/04)
FB falling (AOZ1237-02)
FB falling (AOZ1237-04)

80
85

114

117

77
82

85
90

117

120

82
87

90
95

120

123

87
92

PGOOD Threshold Hysteresis 3 %
PGOOD Fault Delay Time (FB falling) 50 s

Under Voltage Threshold FB falling -30 -25 -20 %
Under Voltage Delay Time 128 s

Over Voltage Threshold FB rising 17 20 23 %

Under Voltage Shutdown Blanking Time VIN = 12V, VEN = 0V, VCC = 5V 20 ms

High-Side NFET On-Resistance VIN = 12V, VCC = 5V 35 45 m

High-Side NFET Leakage V

= 0V, VLX = 0V 10 A

EN

Low-Side NFET On-Resistance VLX = 12V, VCC = 5V 8 12 m

Low-Side NFET Leakage V

= 0V 10 A

EN

Valley Current Limit VCC = 5V 11 A

Thermal Shutdown Threshold

T

J

T

J

rising

falling

145
100

%

%

°C

Rev. 2.0 April 2013

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