UNITRODE UCC2585, UCC3585 Technical data

UNITRODE UCC2585, UCC3585 Technical data

UCC2585

UCC2585

UCC3585

PRELIMINARY

Low Voltage Synchronous Buck Controller

FEATURES

Resistor Programmable 1.25V to 4.5V

VOUT

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

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)

TYPICAL APPLICATION DIAGRAM

VIN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C8

 

 

 

 

 

 

 

 

 

 

 

 

 

0.47 F

R3

 

 

 

 

 

 

 

 

 

R1

 

 

 

27.4k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10k

 

 

 

 

 

 

 

 

 

+

 

+

 

 

15

VIN

CLSET

8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C1

 

C2

 

 

 

 

 

R5

Q1

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

150

F

150

F

 

 

 

 

 

 

 

 

 

1

ENB

PDRV

12

IRF7404

 

 

 

 

 

 

 

C7

 

 

 

 

 

 

 

 

R2

 

 

 

L1 4.7 F

 

 

 

 

 

 

 

147pF

 

 

 

 

 

 

 

 

 

 

549k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

COMP

ISENSE

11

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

R6

 

 

 

 

 

 

 

 

 

 

 

 

Q2

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

 

 

 

IRF7401

+

+

+

 

 

 

 

 

 

4

VFB

NDRV

14

 

 

 

 

 

 

 

C9

C10

C11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10

SD

TRACK

6

 

220 F

220 F

220 F

 

 

 

 

C4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.2N

 

 

 

 

 

 

 

 

R12

R10

 

 

 

 

 

3

SS

N/C

9

 

 

 

 

 

 

 

C5

 

 

 

32k

36k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.22

F

 

 

 

 

 

 

 

 

 

 

 

 

 

16

CT

PWRGND

13

 

 

 

 

 

 

 

 

 

 

C6

 

 

 

 

 

 

 

 

 

 

 

 

 

470pF

 

 

 

 

 

 

 

 

 

 

 

 

 

7

ISET

GND

5

 

 

 

 

R11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R4

 

 

 

 

 

 

 

82k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

100k

 

 

 

 

 

 

 

 

RTN

 

 

 

 

 

 

 

 

 

 

 

 

RTN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UDG-98024

07/99

 

 

 

 

 

 

 

 

 

 

 

 

 

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

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

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

UCC2585

UCC3585

CONNECTION DIAGRAMS

DIL-16, SOIC-16, SSOP-16 (TOP VIEW)

J, N, D, and M Packages

 

 

 

 

 

 

 

 

CT

 

 

 

 

 

 

 

 

ENB

1

 

 

 

 

 

16

 

 

 

 

 

 

 

 

VIN

 

 

 

 

 

 

 

 

COMP

2

 

 

 

 

 

15

SS

 

 

 

 

 

 

 

NDRV

 

 

 

 

 

 

 

3

 

 

 

 

 

14

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VFB

4

 

 

 

 

 

13

PWRGND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GND

5

 

 

 

 

 

12

PDRV

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TRACK

6

 

 

 

 

 

11

ISENSE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ISET

7

 

 

 

 

 

10

SD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CLSET

8

 

 

 

 

 

9

N/C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.

2

UCC2585

UCC3585

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

UCC3585, and TA = –40°C to 85°C for the UCC2585. TA = TJ. VIN = 3.3V, ENB, ISENSE = VIN, VFB = 1.25V, COMP = 1.5V, CT = 330pF, RISET = 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

µ A

VIN Turn On Threshold (UVLO)

 

 

2.35

2.60

V

VIN Turn On Hysteresis

 

 

450

550

mV

Voltage Amplifier Section

 

 

 

 

 

Input Voltage (Internal Reference)

TA = 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) = –50µ A

3.00

3.25

 

V

Output Voltage Low

I(COMP) = 50µ A

 

0.10

0.25

V

Output Source Current

 

–100

–175

 

µ A

Output Sink Current

 

0.4

1.0

 

mA

Oscillator/PWM Section

 

 

 

 

 

Initial Accuracy

TJ = 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, VTRACK = 1.6V

10

12

15

µ A

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

µ A

Current Limit Section

 

 

 

 

 

Pulse to Pulse Threshold

Measured Between VIN and ISENSE

100

125

150

mV

CLSET Current

 

11

14

16

µ A

SD Sink Current

SD = 2V

8

13

18

µ A

SD Source Current

SD = 2V

 

–100

–140

µ A

Restart Threshold

Measured on SDOWN

0.40

0.55

0.90

V

Output Driver Section (PDRV, NDRV)

 

 

 

 

 

Pull Up Resistance

–100mA (Source) TA = 25° C

 

6

 

Pull Down Resistance

100mA (Sink) TA = 25° C

 

4

 

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 = VIN –0.5.

3

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