Fairchild Semiconductor FAN5235 Datasheet

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FAN5235

System Electronics Regulator for Mobile PCs

Features

• Synchronous rectiﬁcation

• ±1% precision internal reference

• >90% efﬁciency

• Input and output voltage feedback

• 5.4V to 24V input voltage range

• Internally set 300kHz ±15% oscillator

• 5V and 3.3V Main outputs switch out of phase

• 5V-ALWAYS and 3.3V-ALWAYS outputs

• Adjustable boost converter for 12V

• Boost converter slaved to 5V Main

• Input UVLO

• Outputs OVP of Buck Converters

• Precision current limit option for 5V, 3.3V Main

• Power Good Voltage Monitor

Applications

• Notebook PCs and PDAs

• Hand-held portable instruments

Description

The FAN5235 is a high efﬁciency and high precision DC/DC controller for notebook converters. Utilization of both input and output voltage feedback in a current-mode control allows for fast and stable loop response over a wide range of input and output voltage variations. The two main regulators switch out of phase to minimize input ripple current.

Current sense based on MOSFET Rdson gives maximum efﬁciency, while also permitting use of a sense resistor for high accuracy. An externally adjustable boost converter can be set to generate 12V.

The F AN5235 is av ailable in a 24-pin QSOP package, and in a 24-pin TSSOP package.

Typical Application

3.3V-ALWAYS@50mA

5V-ALWAYS

3.3V @ 5A +

5V-ALWAYS@ 50mA

SDN3.3

PGOOD

Vin = 5.4-24V

FAN5235

1 VIN 2 3.3 ALW

3 CPUMP3.3 4 HSD3.3

5 SW3.3 6 5V-ALW 7 LSD3.3 8 GND3.3 9 ISEN3.3

10 VFB3.3 11 SDN3.3

12 PGOOD

CPUMP5 24

HSD5 23

SW5 22

ISEN5 21

LSD5 20

GND5 19

VFB5 18

SDN5 17

SW12 16

VFB12 15

SGND 14

SDWN 13

SDN5

VFB12

SDWN

5V-ALWAYS

5V @ 5A

12V @ 120mA

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FAN5235

Pin Assignments

3.3V-ALWA YS

VIN

CPUMP3.3

HSD3.3

SW3.3

5V-ALWA YS

LSD3.3

GND3.3

ISEN3.3

VFB3.3

SDN3.3

PGOOD

Pin Description

Pin Name Pin Number Pin Function Description

VIN 1

3.3V-ALWAYS 2

CPUMP3.3 3

HSD3.3 4

SW3.3 5

5V-ALWAYS 6

LSD3.3 7

GND3.3 8 ISEN3.3 9

VFB3.3 10 SDN3.3

PGOOD 12

SDWN

SGND 14 VFB12 15 SW12 16 SDN5

VFB5 18 GND5 19 LSD5 20

Input power.

3.3V Always on linear regulator. Load current on pins 2 and 6 must not exceed

50mA total.

Charge Pump 3.3V. High side Gate drive voltage for 3.3V. This pin is to be

connected to SW3.3 through a 100nF cap. and to 5V-ALWAYS through a diode

High-side gate driver for 3.3V. Connect this pin directly to the gate of an

N-channel MOSFET. The trace from this pin to the MOSFET gate should be < 1".

High side FET Source and Low Side FET Drain Switching Node. Switching

node for 3.3V.

5V Always on linear regulator output. The sum of the load currents on pins 2

and 6 must not exceed 50mA total.

Low-side gate driver for 3.3V. Connect this pin directly to the gate of an

N-channel MOSFET. The trace from this pin to the MOSFET gate should be < 1".

Ground for 3.3V MOSFET. Current sense for 3.3V. This pin should be connected to the Drain of the bottom

Mosfet with an appropriate resistor and an RC filter. See Application Section.

Voltage feedback for 3.3V. Soft Start and ON/OFF for 3.3V. OFF=GND. ON=open with SDWN=High. Use

open collector device for control.

Power Good Flag. An open collector output that will be logic low if any output

voltage is not above 89% of the nominal output voltage.

Master Shutdown. Shutdown for all power. Off when low. When high

5V/3.3V-ALWAYS are ON while 5V/3.3V-Main are ready to turn on if SDN5, SDN3.3 go open.

Signal ground. Voltage feedback for 12V. FET driver for 12V Boost. Enable/Soft Start for 5V and 12V. Soft start and ON/OFF for 5V & 12V.

OFF=Grounded. ON=open with SDWN

Voltage feedback for 5V. Ground for 5V MOSFET. Low side FET driver for 5V. Connect this pin directly to the gate of an N-channel

MOSFET. The trace from this pin to the MOSFET gate should be < 1".

1 2

3 4

5 6 7 8 9 10

11 12

T op Vie w

24 23 22 21 20 19 18 17 16 15 14

CPUMP5 HSD5 SW5 ISEN5

LSD5 GND5

VFB5 SDN5

SW12 VFB12 SGND

SDWN

=High.

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FAN5235

Pin Description

Pin Name Pin Number Pin Function Description

ISEN5 21

SW5 22

HSD5 23

CPUMP5 24

Absolute Maximum Ratings

SW, ISEN Pins,SDWN Pin -0.3 27 V CPUMP, HSD Pins -0.3 33 V SDN, VFB, V_always pins -0.3 6.5 V CPUMP to SW pins, and all other pins -0.3 6.5 V The sum of the load currents on pins 2 and 6 must not exceed 60mA total

Note:

1. Stresses beyond "Absolute Maximum Ratings" may cause permanent device damage. Continuous exposure to absolute maximum rating conditions may affect device reliability. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specification is not implied.

(Continued)

Current Sense for 5V. This pin should be connected to the drain of the bottom

Mosfet using appropriate resistor and RC filter. See Application Section.

High Side Driver Source and Low Side Driver Drain Switching Node.

Switching node for 5V.

High side FET driver for 5V. Connect this pin directly to the gate of an N-channel

MOSFET. The trace from this pin to the MOSFET gate should be < 1".

Charge Pump 5V. High side Gate drive voltage for 5V. High side Gate drive

voltage for 5V. This pin is to be connected to SW5 through a 100nF cap. and to 5V-ALWAYS through a diode.

Parameter Conditions Min. Typ. Max. Units

-0.3 27 V

Recommended Operating Conditions

Input Voltage, V Ambient Temperature, T

+5.4V to 24V

-20°C to 85°C

Thermal Information

Thermal Resistance, θ Thermal Resistance, θ

Maximum Junction Temperature 150°C Storage Temperature Range -65°C to 150°C Maximum Lead Temperature, Soldering 10 Sec 300°C

88°C/W

QSOP 28.5°C/W

TSSOP 16°C/W

REV. 1.3.3 1/3/02

Ω

FAN5235

ELECTRICAL SPECIFICATIONS

Operating Conditions

Recommended Operating Conditions Unless Noted Refers to Block Diagrams

Parameter Conditions Min. Typ. Max. Units Supply

Input Supply Voltage (DC loading only) Note 1 5.4 24 V

Input Quiescent Current H/LSD Open 1.4 3 mA

Stand-by 300 400 µA

Shut-down <1 5 µA

Input UVLO Threshold Rising Vbat 4.3 4.7 5.1 V

hysteresis 500 mV

5V and 3.3V Main Regulators

Output Voltage Precision 0.1 to 5.5A, 5.4 to 24V -2 +2 % Oscillator Frequency, f

osc

HSD On-Resistance, pull up 7 12 HSD On Resistance pull down 4 10 LSD On-Resistance, pull up 6 9 LSD On Resistance pull down 5 8 HSD On Output, V HSD Off Output, V LSD On Output, V LSD Off Output, V

CPUMP

GS 5V-Always GS

-V

I = 10µA 100 mV I = 10µA 100 mV I = 10µA 100 mV

I = 10µA 100 mV Ramp Amplitude, pk-pk VIN = 16V 2 V Ramp Offset 0.5 V Ramp Gain from V

Error Amplifier GBW 3 MHz Current Limit Threshold R2, R8 = 1K Ω Over Voltage Threshold 2µs delay 110 115 120 %VO Under Voltage Threshold 2µs delay 70 75 80 %VO SDN/SS Full On Voltage Min. (End of Soft Start) 4.2 V SDN/SS Full Off Voltage Max. 800 mV Max Duty Cycle 94 % Min PWM Time 200 nsec VFB3.3 Input Leakage Current 40 55 70 µA

12V Regulator

Output Voltage Precision V_5 =4.9 to 5.1V

and Io=0 to 150mA

FB12

Input Current Note 2 100 200 nA

FB12

Oscillator Frequency (f

/3) 85 100 115 kHz

osc

Gate Drive On-Resistance High or Low 6 12

255 300 345 kHz

125 mV/V

90 135 180 µA

-2 +2 %

2.472 V

Ω

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Ω

FAN5235

Operating Conditions

(Continued)

Recommended Operating Conditions Unless Noted Refers to Block Diagrams

Parameter Conditions Min. Typ. Max. Units 12V Regulator (Continued)

On Output, V Off Output, V

5V-Always GS

-V

I = 10µA 100 mV

I = 10µA 100 mV Ramp Amplitude, pk-pk 2 V Error Amplifier GBW 1 MHz Under Voltage Shut Down 2µs delay 70 76 80 %V Over Voltage Shut Down Measured at VFB

115 %V

O O

Min Duty Cycle 0 % Max Duty Cycle (By design) 32 33 34 %

5V and 3.3V Always

Bypass Switch rdson 1.3 1.5 Linear Regulator Accuracy 5.6 to 24V, 0 to 50mA,

-3.3 2 %

5V Main On or Off

Rated Output Current I

3.3

+ I

050mA Over-current Limit 2µs delay 100 180 mA Under-voltage Threshold 2µs delay 70 75 80 %

Reference

Internal Reference Accuracy 0-70°C -1 1 %

Control Functions

SDWN Off Voltage Max. 800 mV SDWN On Voltage Min. 3 V Over-temperature Shutdown, t

150 °C Over-temperature Hysteresis 25 °C PGOOD Threshold PWM Buck Converters -14 -11 -8.5 %V

PGOOD Sink Current -4 mA PGOOD leakage 1µA +5V Analog Softstart Css=100nF 65 msec +3.3V Analog Softstart Css=100nF 65 msec Soft Start Current 5 µA PGOOD Min Pulse Width Note 2 5 10 µs

Notes

1. The minimum input voltage does not include voltage drop in the source supply due to source resistance. It is operating voltage for static load conditions. To get acceptable load transient performance, the input voltage required will be much higher, in the

7.5 to 8.5 volt range or even higher depending on the severity of dynamic load, source impedance and input and output capacitance and inductor values. The user should thoroughly test the performance at minimum input voltage using intended component values and transient loading.

2. Min/Max specifications are guaranteed by design.

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Fairchild Semiconductor FAN5235 Datasheet

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