Fairchild Semiconductor FAN5038 Datasheet

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FAN5038

Dual Voltage Controller for DSP Power

Features

• Provides complete, low-cost core and I/O power in single chip

• I/O power sequencing

• Core voltage adjustable from 1.5V to 3.6V

• Independent adjustable current limits

• Core up to 13A, I/O up to 5A

• Precision trimmed low TC voltage reference

• Constant On-Time oscillator

• Small footprint 16 lead SOIC package

Applications

• High efﬁciency low-cost power for DSPs

• Power for ASICs and FPGAs

• Programmable dual power supply for high current loads

Description

The FAN5038 provides a complete low-cost power system for DSPs and other loads requiring high-performance. The FAN5038 combines an adjustable switch-mode DC-DC converter for core power with a low-dropout linear regulator for I/O power in a space-saving SO-16 package. Simple external circuitry provides power sequencing and independent current limits. An internal precision voltage reference allows the switcher to be adjusted from 1.5V to 3.6V. With the appropriate external components, the FAN5038 can deliver core power up to 13A, and I/O power up to 5A, allowing multiple DSPs to be powered with a single device.

Block Diagram

Switcher

Select

Linear

Enable

FAN5038

Switching Regulator

Oscillator

1.5V

Reference

Feedback

Control

Digital

Logic

Linear Regulator

+12V +5V

Core

+ –

I/O

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FAN5038 PRODUCT SPECIFICATION

Pin Assignments

LIN_EN

VREF

IFBH

IFBL

FBSW

VCCA

VFBL

GNDP SDRV89

SWCTRL CEXT GNDA VSCL LDRV VCCL VCCP

Pin Descriptions

Name

Number Pin Function Description

LIN_EN 1

VREF 2

IFBH 3

IFBL 4

FBSW 5

VCCA 6

VFBL 7

GNDP 8

SDRV 9

VCCP 10

VCCL 11

LDRV 12

VSCL 13

Linear regulator enable input. Accepts TTL/open collector input levels. A logic level HIGH

on this pin disables the output of the linear regulator.

Voltage reference test point. This pin provides access to the internal precision 1.5V

bandgap reference and should be decoupled to ground using a 0.1µF ceramic capacitor. No load should be connected to this pin.

High side current feedback for switching regulator. 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 Discussion for details.

Low side current feedback for switching regulator. See Applications Discussion for

details.

Voltage feedback for switching regulator. This input is active when a logic level LOW is

input on pin 16 (SWCTRL). Using two external resistors, it sets the output voltage level for the switching regulator. See Applications Discussion for details.

Switching Regulator V

Power supply for switching regulator control circuitry and

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

Voltage feedback for linear regulator. Using two external resistors, this pin sets the

output voltage level for the linear regulator. See Applications Discussion for details.

Power Ground. Return pin for high currents flowing in pins 9, 10 and 12 (SDRV, VCCP and

LDRV). Connect to a low impedance ground. See Applications Discussion for details.

FET driver output for switching regulator. Connect this pin to the gate of the N-channel

MOSFET Q1 as shown in Figure 1. The trace from this pin to the MOSFET gate should be kept as short as possible (less than 0.5"). See Applications Discussion for details.

Switching regulator gate drive V

Power supply for SDRV output driver. Connect to

system 12V supply with R-C filter shown in Figure 1. See Applications Discussion for details.

Linear Regulator Vcc. Power supply for LDRV output op-amp. Connect to system 12V

supply and decouple to ground with 0.1µF ceramic capacitor.

Output driver for linear regulator. Connect this pin to the base of an NPN transistor.

When pin 1 (LIN_EN) is pulled HIGH, the linear regulator is disabled and pin 12 will be pulled low internally.

Low side current sense for linear regulator. Connect this pin between the sense resistor

and the collector of the power transistor. The high side current sense is internally connected to pin 6 (VCCA). Layout is critical to optimal performance of the linear regulator short circuit protection scheme. See Applications Discussion for details.

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FAN5038 PRODUCT SPECIFICATION

Pin Descriptions

Name

GNDA 14

Number Pin Function Description

(continued)

Analog ground. All low power internal circuitry returns to this pin. This pin should be

connected to system ground so that ground loops are avoided. See Applications Discussion for details.

CEXT 15

External capacitor. A 100pF 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 Discussion for details.

SWCTRL 16

Switching regulator control input. Accepts TTL/open collector input levels. A logic level

HIGH on this pin presets the switching regulator output voltage at 3.5V using internal resistors. A logic level LOW on this pin will select the output voltage set by two external resistors and the voltage feedback control pin 5 (VFBSW). See Applications Discussion for details.

Absolute Maximum Ratings

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

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.

+150°C

-65 to +150°C

112°C/W

Operating Conditions

Parameter Conditions Min. Typ. Max. Units

Switching Regulator V Linear Regulator V Logic Inputs, SWCTRL, LIN_EN Logic HIGH

Ambient Operating Temperature, T Drive Gate Supply, V

, VCCA 4.75 5 5.25 V

, VCCL 11.4 12 12.6 V

2.4

CCP

Logic LOW

070°C

9.5 12 12.6 V

0.8

V V

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PRODUCT SPECIFICATION FAN5038

Electrical Characteristics—Switch-Mode Regulator

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

Parameter Conditions Min. Typ. Max. Units

Output Voltage, VOSW

Setpoint Accuracy

Output Temperature Drift T Line Regulation VCCA = 4.75 to 5.25V

Load Regulation I Output Ripple, peak-peak 20MHz BW, I Cumulative DC Accuracy Efficiency I Output Driver Current Open Loop Short Circuit Threshold

Voltage On Time Pulse Width

= 25

C using circuit of Figure 1, unless otherwise noted)

SWCTRL = HIGH

3.5 V

Set by internal resistors

SWCTRL = LOW

1.5 3.6 V

Set by external resistors I

= 4A -1.2 +1.2 %Vo

= 0°C–70°C

40 ppm

0.10 0.15 %Vo

= 4A

= 0 to 4A ±0.9 ±1.3 %Vo

= 4A 15 mV

= 4A 80 %

±55 ±100 mV

0.5 A 70 90 100 mV

= 100pF 2 µs

EXT

Notes:

1. When the SWCTRL pin is HIGH or left open, the switch-mode regulator output will be preset at 3.5V using internal precision resistors. When the SWCTRL pin is LOW, the output voltage may be programmed with external resistors. Please refer to the Applications Section for output voltage selection information.

2. Setpoint accuracy is the initial output voltage variability under the specified conditions. When SWCTRL is LOW, the matching of the external resistors will have a major influence on this parameter.

3. Cumulative DC accuracy includes setpoint accuracy, temperature drift, line and load regulation, and output ripple.

4. The on-time pulse width of the oscillator is preset using external capacitor C curves.

. See Typical Operating Characteristics

EXT

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• ±

•

FAN5038 PRODUCT SPECIFICATION

Electrical Characteristics—Linear Regulator

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

Parameter Conditions Min Typ Max Units

Output Voltage, VOL Setpoint Accuracy

Output Temperature Drift Line Regulation VCCL = 11.4V to 12.6V, I Load Regulation I Output Noise 0.1 to 20KHz 1 mV Cumulative DC Accuracy Crosstalk

Short Circuit Comparator Threshold

Op-amp Output Current Open Loop 50 70 mA

= 25

C using circuit in Figure 1, unless otherwise noted)

Set by external resistors I

=0.5A, using 0.1% resistors -1.5 +1.5 %

1.5 3.6 V

40 ppm

= 0.5A 0.1 0.15 %Vo

= 0 to 5A ±0.7 ±1 %Vo

= 4A 35 mVpp

1.7

40 50 60 mV

Notes:

1. When the LIN_EN pin is LOW, the linear regulator output is set with external resistors. When the LIN_EN pin is HIGH, the linear regulator is disabled and will exhibit no output voltage. Please refer to the Application Section for output voltage selection information.

2. Setpoint accuracy is the initial output voltage variability under the specified conditions. The matching of the external resistors will have a major influence on this parameter.

3. Cumulative DC accuracy includes setpoint accuracy, temperature drift, line and load regulation.

4. Crosstalk is defined as the amount of switching noise from the switch-mode regulator that appears on the output of the linear regulator when both outputs are in a static load condition.

Electrical Characteristics—Common

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

Parameter Conditions Min Typ Max Units

Reference Voltage, VREF 1.485 1.5 1.515 V VREF PSRR 60 dB VCCA Supply Current Independent of load VCCP Supply Current I VCCL Supply Current I

= 25

C using circuit of Figure 1, unless otherwise noted)

= 4A

= 2A

515mA

20 25 mA

5mA

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