Fairchild Semiconductor FAN5037 Datasheet

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FAN5037

Adjustable Switching Regulator Controller

Features

• High power switch-mode DC-DC controller can provide
in excess of 13A

• Output voltage adjustable from 1.2V to 3.6V

• 85% efficiency

• Cumulative accuracy < 3% over line, load, and
temperature variations

• Overvoltage and short circuit protection

• Built-in soft start

• No overshoot at turn-on

Applications

• I/O and AGP power for desktop computers

• High efficiency power for ASICs

• High efficiency power for DSPs

• Adjustable step-down power supplies

Description

The F AN5037 is a high power, switch-mode DC-DC control­ler that provides efficient power for all low-voltage applica­tions. This controller has a built-in Soft Start feature which
offers system protection during power-up by reducing both
inrush current and output overshoot. When combined with
the appropriate external circuitry, the FAN5037 can deliver
load currents as high as 13A at efficiencies as high as 88%.
The FAN5037 can generate output voltages from 1.2V up to

3.6V using external resistors.

The FAN5037 is designed to operate in a constant on-time
control mode under all load conditions. Its accurate low TC
reference eliminates the need for precision external compo­nents in order to achieve the tight tolerance voltage regula­tion required by many applications. Short circuit current
protection is provided through the use of a current sense
resistor, while overvoltage protection is provided internally.

Block Diagram

FAN5037

CEXT

1

Oscillator

1.20V

Reference

VCCA 2

Feedback Control

Digital Logic

GNDP 6

+12V5V+5V

IFBL 4

IFBH 3

VCCP 8

7

DRV

Vout

VFB 5

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FAN5037 PRODUCT SPECIFICATION

Pin Assignments

Pin Descriptions

Pin

Name

CEXT 1

VCCA 2

IFBH 3

IFBL 4

VFB 5

GNDP 6

DRV 7

VCCP 8

Pin

Number Pin Function Description

External capacitor. A 180pF capacitor is connected to this pin as part of the constant

on-time pulse width circuit. Careful layout of this pin is critical to system performance.
See Applications Information for details.

Analog V

system 5V supply and decouple to ground with 0.1µF ceramic capacitor.

High side current feedback. Pins 3 and 4 are used as the inputs for the current feedback

control loop and as the short circuit current sense points. Careful layout of the traces from
these pins to the current sense resistor is critical for optimal performance of the short circuit
protection scheme. See Applications Information for details.

Low side current feedback. See Applications Information for details.
Voltage feedback. Using two external resistors, this pin sets the output voltage level for the

switching regulator.

Power Ground. Connect to a low impedance ground. See Application Information for

details.

MOSFET driver output. Connect this pin to the gate of the N-channel MOSFET Q1 as

shown in Figure 12. The trace from this pin to the MOSFET gate should be kept as short as
possible (less than 0.5"). See Applications Information for details.

Power V

filter shown in Figure 12. See Applications Information for details.

CEXT

VCCA

IFBH

IFBL VFB

Power supply for regulator control circuitry and voltage reference. Connect to

cc

Power supply for DRV output driver. Connect to system 12V supply with R-C

cc

1
2

3
45

FAN5037

VCCP

8

DRV

7

GNDP

6

Absolute Maximum Ratings

Supply V oltages, VCCA 7V
Supply V oltages, VCCP 13V
Junction Temperature, T
Storage Temperature, T

J

S

+150°C

-65 to +150°C
Lead Soldering Temperature, 10 seconds 300°C
Thermal Resistance Junction-to-Ambient, Θ

Note:

1. Functional operation under any of these conditions is not implied. Performance is guaranteed only if Operating Conditions
are not exceeded.

JA

163°C/W

Operating Conditions

Parameter Conditions Min. Typ. Max. Units

Switching Regulator Supply, VCCA 4.75 5 5.25 V
Ambient Operating Temperature, T

A

Gate Drive Supply, VCCP 9.5 12 12.6 V

2

070°C

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•

•

•

•

•

PRODUCT SPECIFICATION FAN5037

Electrical Characteristics

(VCCA = 5V, VCCP = 12V, T
The • denotes specifications which apply over the full ambient operating temperature range.

Parameter Conditions Min. Typ. Max. Units

Output Voltage 1.2 3.6 V
Output Temperature Drift T
Line Regulation VCCA = 4.75 to 5.25V, I
Load Regulation I
V

PSRR VCCA = 4.75 to 5.25V 60 dB

OUT

Output Ripple, peak-peak 20MHz BW, I
Total DC Accuracy

1

Efficiency I
Output Driver Current Open Loop
Short Circuit Threshold Voltage
Undervoltage Lockout
On Time Pulse Width
VCCA Supply Current Independent of load
VCCP Supply Current I

= 25

°

A

C using circuit of Figure 1, unless otherwise noted)

= 0˚C–70˚C 40 ppm/˚C

A

= 13A 3 5 mV

LOAD

= 0 to 5A or 5A to 13A 30 43 mV

LOAD

= 13A 15 mV

LOAD

±55 ±100 mV

= 5A 80 85 %

LOAD

0.5 A
70 90 100 mV

3.5 4.0 4.5 V

2

C

= 180pF 3.5 µs

EXT

515mA

LOAD

= 13A

20 25 mA

Notes:

1. Total DC accuracy includes setpoint accuracy, temperature drift, line and load regulation.

2. The on-time pulse width of the oscillator is set via external capacitor C

EXT

.

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FAN5037 PRODUCT SPECIFICATION

Typical Operating Characteristics

(VCCA = 5V, and T

= +25

A

°

C using circuit in Figure 1, unless otherwise noted)

95
94
93
92
91
90
89
88

Efficiency (%)

87
86
85

12 3 4 5

Efficiency vs. Output Current

678910

Output Current

Output Voltage vs. Temperature, I

+0.50

+0.25

Nom.

-0.25

Output Voltage (%)

-0.50
025

+1.5
+1.0

+0.5

(%)

Nom

OUT

V

50 75

Output Voltage vs. Load

-0.5

-1.0

-1.5
02468

Output Current (A)

= 10A

OUT

100 125

10

Transient Response, 0.5 to 5.5A

(50mV/div)

OUT

(2A/div) V

SW

I

Time (100µs/division)

Output Ripple, I

(10mV/division)

OUT

V

= 10A)

OUT

Time (2µs/division)

4

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