Datasheet

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Document Number: MC34717

Rev 4.0, 12/2008

Freescale Semiconductor

Advance Information

* This document contains certain information on a new product.

Specifications and information herein are subject to change without notice.

5.0 A 1.0 MHz Fully Integrated

Dual Switch-Mode Power

Supply

The 34717 is a highly integrated, space-efficient, low cost, dual

synchronous buck switching regulator with integrated N-channel

power MOSFETs. It is a high performance dual point-of-load (PoL)

power supply with many desired features for the 3.3 and 5.0

environments.

Both channels can provide up to 5.0 A of continuous output current

capability with high efficiency and tight output regulation. The second

channel has the ability to track an external reference voltage in

different configurations.

The 34717 offers the designer the flexibility of many control,

supervisory, and protection functions to allow for easy implementation

of complex designs. It is housed in a Pb-free, thermally enhanced,

and space efficient 26 Pin Exposed Pad QFN.

Features

•50 mΩ integrated N-channel power MOSFETs

• Input voltage operating range from 3.0 to 6.0 V

• ±1% accurate output voltages, ranging from 0.7 to 3.6 V

• The second output has voltage tracking capability in different

configurations

• Programmable switching frequency range from 200 kHz to

1.0 MHz

• Programmable soft start timing

• Over-current limit and short-circuit protection

• Thermal shutdown

• Output over-voltage and under-voltage detection

• Active low power good output signal

• Active low shutdown input

• Pb-free packaging designated by suffix code EP.

Figure 1. 34717 Simplified Application Diagram

DUAL SWITCH-MODE POWER SUPPLY

EP SUFFIX (PB_FREE)

98ASA10728D

26-PIN QFN

34717

ORDERING INFORMATION

Device

Temperature

Range (T

)

Package

MC34717EP/R2 -40 to 85°C 26 QFN

VIN

PVIN1

3.0 TO 6.0 V

BOOT1

SW1

INV1

COMP1

VOUT1

GND

VREFIN

VDDI

FREQ

34717

OUT1

PGND1

PVIN2

BOOT2

SW2

INV2

COMP2

VOUT2

PGND2

ILIM1

MASTER

ILIM2

MCU

OUT2

OUT1

Optional

Summary of content (28 pages)

PAGE 1
Freescale Semiconductor Advance Information Document Number: MC34717 Rev 4.0, 12/2008 5.0 A 1.0 MHz Fully Integrated Dual Switch-Mode Power Supply 34717 The 34717 is a highly integrated, space-efficient, low cost, dual synchronous buck switching regulator with integrated N-channel power MOSFETs. It is a high performance dual point-of-load (PoL) power supply with many desired features for the 3.3 and 5.0 V environments. Both channels can provide up to 5.
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INTERNAL BLOCK DIAGRAM INTERNAL BLOCK DIAGRAM SD PG System Reset M1 Thermal Monitoring System Control Oscillator FREQ FSW Bandgap Regulator VBG Buck Control Logic Discharge ILIM2 ISENSE2 ISENSE1 Current Monitoring VDDI Internal Voltage Regulator ILIM1 VIN ILIM2 ILIM1 BOOT1 M3 BOOT2 VIN PVIN2 M2 VIN PVIN1 M4 SW1 M6 Gate Driver ISENSE FSW FSW Gate I Driver SENSE M5 M7 – VBG INV1 + COMP2 + – + Error Amplifier M8 Discharge PGND2 – + COMP1 PWM Comparator Ramp Genera
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PIN CONNECTIONS ILIM1 ILIM2 FREQ VIN VIN GND VDDI NC PIN CONNECTIONS 26 25 24 23 22 21 20 19 BOOT1 1 18 BOOT2 2 17 PVIN1 PVIN2 PVIN1 PVIN2 Transparent Top View SW1 3 SW2 16 PIN 27 SW1 SW2 PGND2 PGND1 4 15 5 14 VOUT2 PGND1 9 10 VREFIN NC PG 11 12 13 INV2 8 COMP2 7 SD 6 COMP1 PGND2 INV1 VOUT1 Figure 3. 34717 Pin Connections Table 1.
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PIN CONNECTIONS Table 1. 34717 Pin Definitions (continued) A functional description of each pin can be found in the Functional Pin Description section beginning on page 12.
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ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device. Ratings Symbol Value Unit VIN -0.3 to 7.0 V High Side MOSFET Drain Voltage (PVIN1, PVIN2) Pins PVIN -0.3 to 7.0 V Switching Node (SW1, SW2) Pins VSW -0.3 to 7.
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ELECTRICAL CHARACTERISTICS MAXIMUM RATINGS Table 2. Maximum Ratings (continued) All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or permanent damage to the device. Ratings Symbol Value Unit RθJA 93 °C/W RqJMA 32 °C/W RqJB 13.
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ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V, unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions, unless otherwise noted. Characteristic Symbol Min Typ Max Unit VIN 3.0 - 6.0 V IIN - - 35 mA IINOFF - - 100 µA VDDI 2.35 2.5 2.
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ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V, unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions, unless otherwise noted.
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ELECTRICAL CHARACTERISTICS STATIC ELECTRICAL CHARACTERISTICS Table 3. Static Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V, unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions, unless otherwise noted.
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ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS Table 4. Dynamic Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V, unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions, unless otherwise noted. Characteristic Symbol Min Typ Max - 8.0 - - 5.
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ELECTRICAL CHARACTERISTICS DYNAMIC ELECTRICAL CHARACTERISTICS Table 4. Dynamic Electrical Characteristics Characteristics noted under conditions 3.0 V ≤ VIN ≤ 6.0 V, - 40°C ≤ TA ≤ 85°C, GND = 0 V, unless otherwise noted. Typical values noted reflect the approximate parameter means at TA = 25°C under nominal conditions, unless otherwise noted. Characteristic Symbol Min Typ Max Unit (FREQ = GND) FSW - 1.0 - MHz Oscillator Switching Frequency Range FSW 200 - 1000 kHz tPGRESET 8.
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FUNCTIONAL DESCRIPTION INTRODUCTION FUNCTIONAL DESCRIPTION INTRODUCTION Today’s advanced systems are increasingly requiring more efficient and accurate power supplies. They present a set of challenges that include highly accurate voltage regulation, high current and fast transient response capability, voltage monitoring (power sequencing), and increased operating frequency. Point of Load power supplies offer adequate solutions to these challenges.
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FUNCTIONAL DESCRIPTION FUNCTIONAL PIN DESCRIPTION SHUTDOWN INPUT (SD) FREQUENCY ADJUSTMENT INPUT (FREQ) If this pin is tied to the GND pin, the device will be in Shutdown mode. If left unconnected or tied to the VIN pin, the device will be in Normal mode. The pin has an internal pullup of 1.5 MΩ. The buck converters switching frequency can be adjusted by connecting this pin to an external resistor divider between VDDI and GND pins.
PAGE 14
FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION MC34717 - Functional Block Diagram Internal Bias Circuits System Control and Logic Oscillator Protection Functions Control and Supervisory Functions Tracking and Sequencing 2 x Buck Converter Figure 4. Block Illustration INTERNAL BIAS CIRCUITS This block contains all circuits that provide the necessary supply voltages and bias currents for the internal circuitry.
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FUNCTIONAL DESCRIPTION FUNCTIONAL INTERNAL BLOCK DESCRIPTION TRACKING AND SEQUENCING This block allows the second output of the 34717 to track the voltage applied at the VREFIN pin in different tracking configurations. This will be discussed in further details later in this document. For power down during a shutdown mode, the 34717 uses internal discharge MOSFETs (M8 and M9 on Figure 2, page 2) to discharge the first and second output respectively.
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FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES VIN < 3.0 V SD = 0 VOUT2<=VUVF2 VOUT2 Under-voltage VOUT1=ON VOUT2=ON PG = 1 VOUT2>=VOVR2 VOUT2 Over-voltage VOUT1=ON VOUT2=ON PG = 1 TJ >= 170°C Power Off VOUT1=OFF VOUT2=OFF PG = 1 Shutdown FSW is programmed VOUT1 = Discharge VOUT2 = Discharge PG = 1 SD =1 3.0 V<=VIN<=6.
PAGE 17
FUNCTIONAL DEVICE OPERATION OPERATIONAL MODES current that can result in an undesired voltage spike once the capacitor is fully charged. The soft start is active each time the IC goes out of standby or shutdown mode, power is recycled, or after a fault retry.
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TYPICAL APPLICATIONS TYPICAL APPLICATIONS VIN FREQ ILIM2 ILIM1 C14 0.1 μF VDDI 4 C27 0.1 μF VOUT1 VOUT1 6 7 ILIM1 ILIM2 FREQ VIN VIN 8 9 10 PG C13 0.1 μF Compensation Network SW1 14 VOUT2 C11 0.1 μF VOUT2 11 12 13 INV1 COMP1 VREFIN PGND2 15 PGND2 PGND1 SW2 15 PGND2 PGND1 PVIN2 16 SW2 INV1 5 17 16 SW2 MC34717 SW1 SW2 0.
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TYPICAL APPLICATIONS Figure 6. 34717 Typical Application I/O Signals VIN Capacitors VIN J2 PVIN1 VO1 3 2 1 GND PVIN2 VO2 GND 3 2 1 VM VIN GND 3 2 1 PGOOD LED VMASTER VM VIN C17 10 μF C16 0.
PAGE 20
TYPICAL APPLICATIONS CONFIGURING THE OUTPUT VOLTAGE: Both channels for the 34717 are general purpose DC-DC converters. The resistor divider to the INV node is responsible for setting the output voltage. The equation is: VOUT ⎛ R1 ⎞ = V REF ⎜ + 1⎟ ⎝ R2 ⎠ For channel 1: VREF=VBG=0.7V. For channel 2: The second channel of the 34717 has an internal reference selector, thus VREF can be either the voltage at VREFIN terminal or the internal reference voltage VBG.
PAGE 21
TYPICAL APPLICATIONS SELECTING INDUCTOR The Inductor calculation process is the same for both Channels. The equation is the following: (VOUT + I OUT * ( Rds(on) _ ls + r _ w)) ΔI OUT VOUT Maximum Off Time Percentage = 1− Vin _ max L = D'MAX ∗T ∗ D 'MAX T Switching Period Rds(on) _ ls Drain – to – Source Resistance of FET r_w ΔI OUT Winding Resistance of Inductor Output Current Ripple dt _ I _ rise = T * I OUT ΔI OUT _ step The following formula is helpful to find the maximum allowed ESR.
PAGE 22
TYPICAL APPLICATIONS 5. Equating pole 2 to 5 times the Crossover Frequency achieves a faster response and a proper phase margin SWx Lx VOUTx RSx COx R1x CSx INVx CXx RFx 5 • F CROSS = F 1 --------------------------------------P2 = CF CX 2π • R F -------------------CF + Cx R2x CFx CX = COMPx CF 2π * R F C F FP 2 − 1 Figure 9. Type III compensation network 1. Choose a value for R1 TRACKING CONFIGURATIONS. 2.
PAGE 23
TYPICAL APPLICATIONS resistors will affect the accuracy of the system and must be 1% accurate resistors. To achieve this tracking configuration, the master voltage must be connected in the way shown and cannot be directly connected to the VREFIN terminal. and R2 = R4 + R5). The master’s feedback resistor divider would be (R3+R4) and R5. All five resistors will affect the accuracy of the system and must be 1% accurate resistors.
PAGE 24
TYPICAL APPLICATIONS LAYOUT GUIDELINES possible. Other critical small signal components include the bypass capacitors for VIN, VREFIN, and VDDI. Locate the bypass capacitors as close to the pin as possible. The use of a multi-layer printed circuit board is recommended. Dedicate one layer, usually the layer under the top layer, as a ground plane. Make all critical component ground connections with vias to this layer.
PAGE 25
PACKAGING PACKAGING DIMENSIONS PACKAGING PACKAGING DIMENSIONS EP SUFFIX (PB_FREE) 26-PIN QFN 98ASA10728D ISSUE 0 34717 Analog Integrated Circuit Device Data Freescale Semiconductor 25
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PACKAGING PACKAGING DIMENSIONS EP SUFFIX (PB-FREE) 26-PIN QFN 98ASA10728D ISSUE 0 34717 26 Analog Integrated Circuit Device Data Freescale Semiconductor
PAGE 27
REVISION HISTORY REVISION HISTORY REVISION DATE DESCRIPTION OF CHANGES 1.0 2/2006 • • Pre-release version Implemented Revision History page 2.0 1/2007 • • • Initial release Converted format from Market Assessment to Product Preview Major updates to the data, form, and style 3.
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How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. Technical Information Center, EL516 2100 East Elliot Road Tempe, Arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.