Texas Instruments UCC3585N, UCC3585MTR, UCC3585M, UCC3585DTR, UCC3585D Datasheet

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UCC2585 UCC3585

PRELIMINARY

DESCRIPTION

The UCC2585/UCC3585 synchronous Buck controller provides flexible high efficiency power conversion for output voltages as low as 1.25V with guaranteed ±1% DC accuracy. Output currents are only limited by the choice of external logic level MOSFETs. With an input voltage range of

2.5V to 6.0V it is the ideal choice for 3.3V only, battery input, or other low voltage systems. Applications include local microprocessor core voltage power supplies for desktop and Notebook computers, and high speed GTL bus regulation.Its fixed frequency oscillator is capable of providing practical PWM operation to 700kHz.

With its low voltage capability and inherent “always on” operation, the UCC2585/UCC3585 causes VOUT to track VIN once VIN has exceeded the threshold voltage of the external P channel MOSFET. Tracking can be tailored for any application with a single resistor or disabled by connecting TRACK to VIN. For dual supply rail microprocessors this feature negates the need for external diodes to insure supply voltage tracking between the +3.3V and lower voltage microprocessor core supplies.

(continued)

Low Voltage Synchronous Buck Controller

FEATURES

•

Resistor Programmable 1.25V to 4.5V V

OUT

•

2.5V to 6V Input Supply Range

•

1% DC Accuracy

•

High Efficiency Synchronous Switching

•

Drives P-channel (High Side) and N-channel (Low Side) MOSFETs

•

Lossless Programmable Current Limit

•

Logic Compatible Shutdown

•

Programmable Frequency

•

Start-up Voltage Tracking Protects Dual Rail Microprocessors

07/99

PDRV

CLSET

ISENSE

NDRV

PWRGND

TRACK

N/C

15 VIN

VFB

ENB

COMP

3 SS

GND

ISET

0.47µF

Q1 IRF7404

Q2 IRF7401

L1 4.7µF

220µF

C10

220µF

C11

VOUT

RTN

VIN

220µF

100k

549k

10k

27.4k

R12

32k

R10

36k

R11

82k

470pF

0.22µF

3.2N

147pF

150µFC2150µF

TYPICAL APPLICATION DIAGRAM

UDG-98024

UCC2585 UCC3585

DIL-16, SOIC-16, SSOP-16 (TOP VIEW) J, N, D, and M Packages

ABSOLUTE MAXIMUM RATINGS

Analog Pins

Minimum and Maximum Forced Voltage

(Reference to GND) . . . . . . . . . . . . . . . . . . . –0.3V to +6.3V

Digital Pins

Minimum and Maximum Forced Voltage

(Reference to GND) . . . . . . . . . . . . . . . . . . . . .–0.3V to 6.3V

Power Driver Output Pins

Maximum forced current . . . . . . . . . . . . . . . . . . . . . . . . . ±1.0A

Operating Junction Temperature. . . . . . . . . . –55°C to +125°C

Storage Temperature. . . . . . . . . . . . . . . . . . . –65°C to +150°C

Note: Unless otherwise indicated, voltages are reference to ground and currents are positive into, negative out of, the spec

ified terminals. Pulsed is defined as a less than 10% duty cycle with a maximum duration of 500ns.

NDRV

VIN

PWRGND

PDRV

ISENSE

N/C

COMP

ENB

CLSET

TRACK

ISET

VFB

GND

CONNECTION DIAGRAMS

DESCRIPTION (cont.)

The UCC2585/UCC3585 drives a complementary pair of power MOSFET transistors, P-channel on the high side, and N-channel on the low side to step down the input voltage at up to 90% efficiency.

A programmable two-level current limiting function is provided by sensing the voltage drop across the high side P channel MOSFET. This circuit can be configured to pro

vide pulse-by-pulse limiting, timed shutdown after 7 con

secutive faults, or latch-off after fault detection, allowing maximum application flexibility. The current limit threshold is programmed with a single resistor selected to match system MOSFET characteristics.

The UCC2585/UCC3585 also includes undervoltage lockout, a logic controlled enable, and softstart functions. The UCC2585/UCC3585 is offered in the 16 pin surface mount and through hole packages.

APPLICATIONS

•

Low Voltage Microprocessor Power such as PowerPC 603 and 604

•

High Power 5V or 3.3V to 1.25V–4.5V Regulators

• GTL Bus Termination

UCC2585 UCC3585

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated, these specifications hold for TA= 0°C to 70°C for the

UCC3585, and T

= –40°C to 85°C for the UCC2585. TA=TJ. VIN = 3.3V, ENB, I

SENSE

= VIN,VFB= 1.25V, COMP = 1.5V,

= 330pF, R

ISET

= 100k, RTRACK = 10k, RCLSET = 10k.

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Input Supply Section

Supply Current – Total (Active) 2.3 3.5 mA Supply Current – Shutdown ENABLE = 0V 10 25 µA VIN Turn On Threshold (UVLO) 2.35 2.60 V VIN Turn On Hysteresis 450 550 mV

Voltage Amplifier Section

Input Voltage (Internal Reference) T

= 0°C to 70°C, VIN = 3.0V to 3.6V, Note 1 1.238 1.250 1.262 V Input Voltage (Internal Reference) VIN = 3.0V to 3.6V, IND/MIL Temp, Note 1 1.228 1.250 1.273 V Open Loop Gain COMP = 0.5 to 2.5V 65 80 dB Output Voltage High I(COMP) = –50µA 3.00 3.25 V Output Voltage Low I(COMP) = 50µA 0.10 0.25 V Output Source Current –100 –175 µA Output Sink Current 0.4 1.0 mA

Oscillator/PWM Section

Initial Accuracy T

= 25°C 405 450 495 kHz Initial Accuracy Over Temperature 390 450 510 kHz CT Ramp Peak to Valley 1.8 2.1 2.4 V CT Ramp Valley Voltage 0.3 0.4 V PWM Maximum Duty Cycle COMP = 3V, Measured on PDRV 100 % PWM Minimum Duty Cycle COMP = 0.2V, Measured on PDRV 0 % PWM Delay to Outputs COMP = 2.5V 45 ns Tracking Current Measured on TRACK, V

TRACK

= 1.6V 10 12 15 µA Enable High Threshold Measured on ENABLE (Note 3) 2.8 V Enable Low Threshold Measured on ENABLE 0.5 V Softstart Charge Current SS = 0V –10 –14 –18 µA

Current Limit Section

Pulse to Pulse Threshold Measured Between V

and I

SENSE

100 125 150 mV CLSET Current 11 14 16 µA SD Sink Current SD = 2V 8 13 18 µA SD Source Current SD = 2V –100 –140 µA Restart Threshold Measured on SDOWN 0.40 0.55 0.90 V

Output Driver Section (PDRV, NDRV)

Pull Up Resistance –100mA (Source) T

= 25°C6Ω

Pull Down Resistance 100mA (Sink) T

= 25°C4Ω

Deadtime Delay Note 2 150 200 250 ns

Note 1. Measured on COMP with the Error Amp in a Unity Gain (voltage follower) configuration. Note 2. 50% point of PDRV Rise to NDRV Rise and 50% point of NDRV Fall to PDRV Fall. Note 3. Enable High Threshold = V

–0.5.

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