UNITRODE UCC2585, UCC3585 Technical data
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Low Voltage Synchronous Buck Controller
UCC2585
UCC3585
PRELIMINARY
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
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
R1
C7
C4
3.2N
10k
R2
549k
C5
0.22µF
C6
470pF
15 VIN
1
2
4
10
3 SS
16
7
R4
100k
RTN
++
C1
150µFC2150µF
147pF
ENB
COMP
VFB
SD
CT
ISET
C8
0.47µF
CLSET
PDRV
ISENSE
NDRV
TRACK
N/C
PWRGND
GND
R3
27.4k
8
R5
3
12
11
R6
3
14
6
9
13
5
Q1
IRF7404
L1 4.7µF
Q2
IRF7401
+
C9
220µF
++
220µF
C10
C11
220µF
R12
32k
R10
36k
R11
82k
VOUT
RTN
07/99
UDG-98024
UCC2585
UCC3585
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.
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
CONNECTION DIAGRAMS
DIL-16, SOIC-16, SSOP-16 (TOP VIEW)
J, N, D, and M Packages
ENB
1
SS
VFB
GND
ISET
2
3
4
5
6
7
8
COMP
-
TRACK
CLSET
16
15
14
13
12
11
10
9
CT
VIN
NDRV
PWRGND
PDRV
ISENSE
SD
N/C
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.
2
UCC2585
UCC3585
ELECTRICAL CHARACTERISTICS:
UCC3585, and T
C
= 330pF, R
T
= –40°C to 85°C for the UCC2585. TA=TJ. VIN = 3.3V, ENB, I
A
= 100k, RTRACK = 10k, RCLSET = 10k.
ISET
Unless otherwise stated, these specifications hold for TA= 0°C to 70°C for the
= VIN,VFB= 1.25V, COMP = 1.5V,
SENSE
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
A
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
J
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
= 1.6V 10 12 15 µA
TRACK
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
IN
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
Pull Down Resistance 100mA (Sink) T
= 25°C6Ω
A
= 25°C4Ω
A
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
IN
–0.5.
3
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