Fairchild FAN2103 service manual

September 2011

FAN2103 — TinyBuck™ 3A, 24V Input, Integrated Synchronous Buck Regulator

Features

 3A Output Current  Over 95% Efficiency  Fully Synchronous Operation with Integrated

Schottky Diode on Low-side MOSFET Boosts Efficiency

 Programmable Frequency Operation (200KHz to

600KHz)

 Power-good Signal  Accepts Ceramic Capacitors on Output  External Compensation for Flexible Design  Wide Input Range: 3V to 24V  Output Voltage Range: 0.8V to 90%V

IN

 Input Under-Voltage Lockout  Programmable Over-Current Limit  Under-Voltage, Over-Voltage, and

Thermal Protections

 5x6mm, 25-pin, 3-Pad MLP

Applications

 Graphics Cards  Battery-powered Equipment  Set-top Boxes  Point-of-load Regulation  Servers

Description

The FAN2103 TinyBuck™ is an easy-to-use, cost- and space-efficient, 3A synchronous buck solution. It enables designers to solve high current requirements in a small area with minimal external components.

External compensation, programmable switching frequency, and current limit features allow for design optimization and flexibility.

The summing current mode modulator uses lossless current sensing for current feedback and over-current, and includes voltage feedforward.

Fairchild’s advanced BiCMOS power process, combined with low R efficient MLP package provide the ability to dissipate high power in a small package.

Output over-voltage, under-voltage, and thermal shutdown protections plus power-good, help protect the devices from damage during fault conditions.

internal MOSFETs and a thermally

DS(ON)

Related Application Notes

 TinyCalc™ Design Tool  AN-6033 — TinyCalc™ Design Tool Guide  AN-5067 – PCB Land Pattern Design and Surface

Mount Guidelines for MLP Packages

Ordering Information

Part Number

FAN2103MPX -10°C to 85°C 25-Pin Molded Leadless Package (MLP) 5x6mm Tape and Reel

FAN2103EMPX -40°C to 85°C 25-Pin Molded Leadless Package (MLP) 5x6mm Tape and Reel

Operating

Temperature Range

Package Packing Method

Typical Application Diagram

FAN2103 — TinyBuck™ 3A, 24V Input, Integrated Synchronous Buck Regulator

Block Diagram

CC

V

ILIM

COMP

FB

SS

EN

RAMP

OSC

VREF

Def Level

Error Amplifier

RAMP

GEN

IILIM

Figure 1. Typical Application

Current Limit Comparator

PWM Comparator

Summing Amplifier

RSQ

Current

Sense

Figure 2. Block Diagram

Boot

Diode

Gate

Drive

Circuit

BOOT

V

IN

SW

GND

CBOOT

L

VOUT

C

OUT

Pin Configuration

FAN2103 — TinyBuck™ 3A, 24V Input, Integrated Synchronous Buck Regulator

Figure 3. MLP 5x6mm Pin Configuration (Bottom View)

Pin Definitions

Pin Name Description

P1, 6-12 SW

P2, 2-5 VIN

P3, 21-23 PGND

1 BOOT

13 PGOOD

14 EN

15 VCC

16 AGND

17 ILIM

18 R(T)

19 FB

20 COMP

24 NC

25 RAMP

Switching Node. Power Input Voltage. Connect to the main input power source. Power Ground. Power return and Q2 source. High-side Drive BOOT Voltage. Connect through capacitor (C

an internal synchronous bootstrap diode to recharge the capacitor on this pin to VCC when SW is LOW.

Power-Good Flag. An open-drain output that pulls LOW when FB is outside a ±10% range

of the reference when EN is HIGH. PGOOD does not assert HIGH until the fault latch is enabled.

ENABLE. Enables operation when pulled to logic HIGH or left open. Toggling EN resets the

regulator after a latched fault condition. This input has an internal pull-up when the IC is functioning normally. When a latched fault occurs, EN is discharged by a current sink.

Input Bias Supply for IC. The IC’s logic and analog circuitry are powered from this pin. Analog Ground. The signal ground for the IC. All internal control voltages are referred to

this pin. Tie this pin to the ground island/plane through the lowest impedance connection.

Current Limit. A resistor (R

limit trip threshold lower than the default setting.

Oscillator Frequency. A resistor (R

frequency.

Output Voltage Feedback. Connect through a resistor divider to the output voltage. Compensation. Error amplifier output. Connect the external compensation network between

this pin and FB.

No Connect. This pin is not used. Ramp Amplitude. A resistor (R

and provides voltage feedforward functionality.

) to SW. The IC includes

BOOT

) from this pin to AGND can be used to program the current-

ILIM

) from this pin to AGND sets the PWM switching

T

) connected from this pin to VIN sets the ramp amplitude

RAMP

FAN2103 — TinyBuck™ 3A, 24V Input, Integrated Synchronous Buck Regulator

Absolute Maximum Ratings

Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only.

Parameter Conditions Min. Max. Unit

VIN to PGND 28 V

VCC to AGND AGND = PGND 6 V

BOOT to PGND 35 V

BOOT to SW -0.3 6.0 V

SW to PGND Transient (t < 20ns, f < 600KHz) -5 30 V

All other pins -0.3 VCC+0.3 V

ESD

Human Body Model, JEDEC JESD22-A114 2.0

Charged Device Model, JEDEC JESD22-C101 2.5

kV

Recommended Operating Conditions

The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to absolute maximum ratings.

Symbol Parameter Conditions Min. Typ. Max. Unit

VCC Bias Voltage VCC to AGND 4.5 5.0 5.5 V

VIN Supply Voltage VIN to PGND 3 24 V

TA Ambient Temperature

TJ Junction Temperature +125 °C

FAN2103M -10 +85 °C

FAN2103EM -40 +85 °C

Thermal Information

Symbol Parameter Min. Typ. Max. Unit

T

Storage Temperature -65 +150 °C

STG

TL Lead Soldering Temperature, 10 Seconds +300 °C

TVP Vapor Phase, 60 Seconds +215 °C

TI Infrared, 15 Seconds +220 °C

P1 (Q2) 4 °C/W

JC



J-PCB

PD Power Dissipation, TA = 25°C 2.8

Note:

1. Typical thermal resistance when mounted on a four-layer, two-ounce PCB, as shown in Figure 25. Actual results are dependent on mounting method and surface related to the design.

Thermal Resistance: Junction-to-Case

Thermal Resistance: Junction-to-Mounting Surface 35

P2 (Q1) 7 °C/W

P3 4 °C/W

(1)

°C/W

(1)

W

Electrical Specifications

Recommended operating conditions are the result of using the circuit shown in Figure 1 unless otherwise noted.

Parameter Conditions Min. Typ. Max. Unit

Power Supplies

SW = Open, FB = 0.7V, V f

= 600KHz

VCC Current

SW

Shutdown: EN = 0, VCC = 5V 7 10 µA

VCC UVLO Threshold

Rising VCC 4.1 4.3 4.5 V

Hysteresis 300 mV

Oscillator

Frequency

RT = 50K

RT = 24K

Minimum On-Time

Ramp Amplitude, pk–pk

Minimum Off-Time

(2)

50 65 ns

, 1.8V

16V

IN

= 200K

R

(2)

100 150 ns

RAMP

, RT = 30K,

OUT

Reference

Reference Voltage (VFB)

Temperature Coefficient

FAN2103M, 25°C 794 800 806 mV

FAN2103EM, 25°C 795 800 805 mV

FAN2103M, -10 to +85°C 50 PPM

FAN2103EM, -40 to +85°C 70 PPM

Error Amplifier

DC Gain

Gain Bandwidth Product

Output Voltage (V

Output Current, Sourcing V

Output Current, Sinking V

(2)

12 15 MHz

) 0.4 3.2 V

COMP

V

= 5V

CC

= 5V, V

CC

= 5V, V

CC

= 2.2V 1.5 2.2 mA

COMP

= 1.2V 0.8 1.2 mA

COMP

FB Bias Current VFB = 0.8V, 25°C -850 -650 -450 nA

Protection and Shutdown

Current Limit R

I

Current 25°C, VCC = 5V 9 10 11 µA

LIM

Over-Temperature Shutdown

Over-Temperature Hysteresis +30 °C

open 3.8 5.0 7.0 A

ILIM

Internal IC Temperature

Over-Voltage Threshold 2 Consecutive Clock Cycles 110 115 120 %V

Under-Voltage Shutdown 16 Consecutive Clock Cycles 68 73 78 %V

Fault Discharge Threshold Measured at FB Pin 250 mV

Fault Discharge Hysteresis Measured at FB Pin (VFB ~500mV) 250 mV

Soft-Start

V

to Regulation (T0.8)

OUT

Fault Enable/SSOK (T1.0) 6.7 ms

Frequency = 600KHz

Note:

2. Specifications guaranteed by design and characterization; not production tested.

= 5V,

CC

8 12 mA

255 300 345 KHz

540 600 660 KHz

0.53 V

80 85 dB

+160 °C

OUT

5.3 ms

FAN2103 — TinyBuck™ 3A, 24V Input, Integrated Synchronous Buck Regulator

Fairchild FAN2103 service manual

Specifications and Main Features

Frequently Asked Questions

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