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UCC2915 UCC3915
15V Programmable Hot Swap Power Manager
FEATURES
* Integrated 0.15 Ohm Power MOSFET * 7V to 15V Operation * Digital Programmable Current Limit from 0A to 3A * 100 A ICC when Disabled * Programmable ON Time * Programmable Start Delay * Fixed 2% Duty Cycle * Thermal Shutdown * Fault Output Indicator * Maximum Output Current can be set to 1A above the Programmed Fault Level or to a full 4A * Power SOIC and TSSOP, Low Thermal Resistance Packaging
DESCRIPTION
The UCC3915 Programmable Hot Swap Power Manager provides complete power management, hot swap capability, and circuit breaker functions. The only external component required to operate the device, other than power supply bypassing, is the fault timing capacitor, CT. All control and housekeeping functions are integrated, and externally programmable. These include the fault current level, maximum output sourcing current, maximum fault time, and startup delay. In the event of a constant fault, the Internal fixed 2% duty cycle ratio limits average output power. The internal 4 bit DAC allows programming of the fault level current from 0 to 3A with 0.25A resolution. The IMAX control pin sets the maximum sourcing current to 1A above the trip level or to a full 4A of output current for fast output capacitor charging. When the output current is below the fault level, the output MOSFET is switched ON with a nominal ON resistance of 0.15 . When the output current exceeds the fault level, but is less than the maximum sourcing level, the output remains switched ON, but the fault timer starts, charging CT. Once CT charges to a preset threshold, the switch is turned OFF, and remains OFF for 50 times the programmed fault time. When the output current reaches the maximum sourcing level, the MOSFET transitions from a switch to a constant current source.
BLOCK DIAGRAM
2 CHARGE PUMP MAX CURRENT LEVEL LINEAR CURRENT AMPLIFIER OVER CURRENT COMPARATOR REVERSE VOLTAGE COMPARATOR 30mV + 3 CURRENT SENSE H = OPEN POWER FET * VIN
IMAX 10
H = 4A
VOUT
4A
1A ABOVE FAULT CURRENT FAULT LEVEL 0-3 AMPS
ON TIME CONTROL 2% DUTY CYCLE
14 VOUT 15
0-3A 0.25 RES
THERMAL SHUTDOWN INTERNAL BIAS + -
1.5V
1
SHTDWN
6 B3
7 B2
8 B1
9 B0
5 GND
4
13
12
11 CT
16 FAULT * BODY DIODE
4 BIT DAC
HEAT SINK GND PINS
Note: Pin numbers refer to DIL-16 and SOIC-16 packages.
UDG-99174
SLUS198A - FEBRUARY 2000
UCC2915 UCC3915
ABSOLUTE MAXIMUM RATINGS
VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +15.5 Volts VOUT VIN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3V FAULT Sink Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA FAULT Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 to 8V Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Limiting TTL Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 to VIN Storage Temperature . . . . . . . . . . . . . . . . . . . 65 C to +150 C Junction Temperature . . . . . . . . . . . . . . . . . . . 55 C to +150 C Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300 C
(continued)
DESCRIPTION (cont.)
The UCC3915 can be put into sleep mode, drawing only 100 A of supply current. Other features include an open drain Fault Output Indicator, Thermal Shutdown, Under-
Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages.
CONNECTION DIAGRAMS
DIL-16, SOIC-16 (Top View) N, DP Package
SHTDWN VIN VIN GND* EGND* B3 B2 B1 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 FAULT VOUT VOUT GND* GND*
GND* 7 8 9 10 11 12 18 17 16 15 14 13 GND* GND* N/C CT IMAX B0
PWP-24 (Top View) TSSOP Package
SHTDWN VIN VIN N/C GND* GND* 1 2 3 4 5 6 24 23 22 21 20 19 FAULT VOUT VOUT N/C GND* GND*
CT IMAX B0
GND* EGND* B3 B2 B1
*Pin 5 serves as lowest impedance to the electrical ground; Pins 4, 12, and 13 serve as heat sink/ground. These pins should be connected to large etch areas to help dissipate heat. For N Package, pins 4, 12, and 13 are N/C.
*Pin 9 serves as lowest impedance to the electrical ground; other GND pins serve as heat sink/ground. These pins should be connected to large etch areas to help dissipate heat.
ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 40C to +85C for the UCC2915 and 0C to 70C for the UCC3915, VIN = 12V, IMAX = 0.4V, SHTDWN = 2.4V, TA = TJ.
PARAMETER Supply Section Voltage Input Range Supply Current Sleep Mode Current Output Leakage Output Section Voltage Drop IOUT = 1A (10V to 12V) IOUT = 2A (10V to 12V) IOUT = 3A (10V to 12V) 0.15 0.3 0.45 0.3 0.6 0.9 V V V SHTDWN = 0.2V, No load SHTDWN = 0.2V 7.0 1.0 100 15.0 2.0 150 20 V mA A A TEST CONDITIONS MIN TYP MAX UNITS
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UCC2915 UCC3915 ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for TA = 40C to +85C for the UCC2915 and 0C to 70C for the UCC3915, VIN = 12V, IMAX = 0.4V, SHTDWN = 2.4V, TA = TJ.
PARAMETER Output Section (cont.) Voltage Drop (cont). IOUT = 1A, VIN = 7V and 15V IOUT = 2A, VIN = 7V and 15V IOUT = 3A, VIN = 7V, 12V Max. Initial Startup Time Short Circuit Response Thermal Shutdown Thermal Hysteresis DAC Section Trip Current Code = 0000-0011 (Device Off) Code = 0100 Code = 0101 Code = 0110 Code = 0111 Code = 1000 Code = 1001 Code = 1010 Code = 1011 Code = 1100 Code = 1101 Code = 1110 Code = 1111 Max Output Current Over Trip (Current Source Mode) Code = 0100 to 1111, IMAX = 0V Max Output Current (Current Source Mode) Fault Output Section CT Charge Current CT Discharge Current Output Duty Cycle CT Fault Threshold CT Reset Threshold Shutdown Section Shutdown Threshold Shutdown Hysteresis Input Current Open Drain Output Section High Level Output Current Low Level Output Voltage TTL Input DC Characteristics Section TTL Input Voltage High TTL Input Voltage Low TTL Input High Current TTL Input Low Current VIH = 2.4V VIL = 0.4V 3 2.0 0.8 10 1 V V A A FAULT = 5V IOUT = 5mA 0.2 250 0.8 A V 1.1 1.5 150 100 500 1.9 V mV nA VCT = 1.0V VCT = 1.0V VOUT = 0V 83 0.8 1.0 1.2 0.4 -62 1.2 1.9 1.5 0.5 47 1.8 3.3 1.7 0.6 A A % V V Code = 0100 to 1111, IMAX = 2.4V 0.07 0.32 0.50 0.75 1.0 1.25 1.5 1.70 1.90 2.1 2.30 2.50 0.35 3.0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.0 1.0 4.0 0.45 0.70 0.98 1.3 1.6 1.85 2.15 2.4 2.7 2.95 3.25 3.50 1.65 5.2 A A A A A A A A A A A A A A Note 2 Note 2 Note 2 Note 2 0.2 0.4 0.6 100 100 165 10 0.4 0.8 1.2 V V V s ns C C TEST CONDITIONS MIN TYP MAX UNITS
Note 1: All voltages are with respect to GND. Current is positive into and negative out of the specified terminal. Note 2: Guaranteed by design. Not 100% tested in production.
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UCC2915 UCC3915 PIN DESCRIPTIONS
SB0 - B3: These pins provide digital input to the DAC, which sets the fault current threshold. They can be used to provide a digital soft-start and adaptive current limiting. CT: A capacitor connected to ground sets the maximum fault time. The maximum fault time must be more than the time required to charge the external capacitance in one cycle. The maximum fault time is defined as TFAULT = 3 16.1 10 CT. Once the fault time is reached the output 3 CT, will shutdown for a time given by TSD = 833 10 this equates to a 1.9% duty cycle. FAULT: Open drain output, which pulls low upon any fault or interrupt condition, Fault, or Thermal Shutdown. IMAX: When this pin is set to a logic low, the maximum sourcing current will always be 1A above the programmed fault level. When set to a logic high, the maximum sourcing current will be a constant 4A for applications which require fast charging of load capacitance. SHTDWN: When this pin is brought to a logic low, the IC is put into a sleep mode drawing typically less than 100 A of ICC.The input threshold is hysteretic, allowing the user to program a startup delay with an external RC circuit. VIN: Input voltage to the UCC3915. The recommended voltage range is 7 to 15 volts. Both VIN pins should be connected together and connected to power source. VOUT: Output voltage from the UCC3915. Both VOUT pins should be connected together and connected to the load. When switched the output voltage will be approxiIOUT). VOUT must not exceed VIN mately VIN - (0.15 by greater than 0.3V.
APPLICATIONS INFORMATION
4 VIN 2 +5V R1 LED 16 FAULT 11 CT CT B0 9 B1 8 B2 7 VIN CIN D1 3
12
13
5 GND 14 VOUT 15 RL COUT RSD VIN VOUT
HEAT SINK GND PINS
UCC3915 S6 SHTDWN 1 CSD B3 6 IMAX 10 VIN DIP SWITCH
UDG-99175
S1
S2
S3
S4
S5
Figure 1. Evaluation circuit.
* Reducing the power distribution inductance (e.g., twist the positive (+) and negative (-) leads of the power supply feeding VIN, locate the power supply close to the UCC3915 or use a PCB ground plane). * Decoupling VIN with a capacitor, CIN (refer to Fig. 1), located close to the VIN pin. This capacitor is typically less than 1 F to limit the inrush current. * Clamping the voltage at VIN below 15V with a Zener diode, D1(refer to Fig. 1), located close to the VIN pin. 4
Protecting The UCC3915 From Voltage Transients The parasitic inductance associated with the power distribution can cause a voltage spike at VIN if the load current is suddenly interrupted by the UCC3915. It is important to limit the peak of this spike to less than 15V to prevent damage to the UCC3915. This voltage spike can be minimized by:
UCC2915 UCC3915 APPLICATION INFORMATION (cont.)
UDG-94138
Estimating Maximum Load Capacitance For hot swap applications, the rate at which the total output capacitance can be charged depends on the maximum output current available and the nature of the load. For a constant-current, current-limited application, the output will come up if the load asks for less than the maximum available short-circuit current. To guarantee recovery of a duty-cycle from a shortcircuited load condition, there is a maximum total output capacitance which can be charged for a given unit ON time (Fault time). The design value of ON or Fault time can be adjusted by changing the timing capacitor CT. For worst-case constant-current load of value just less than the trip limit; COUT(max) can be estimated from:
16 .1 * 10 3 * CT COUT (max) (IMAX - ILOAD ) * VOUT Where VOUT is the output voltage. For a resistive load of value RI, the value of COUT(max) can be estimated from: 16 .1 * 10 3 * CT 1 RL * n VOUT 1 - I MAX * R L
COUT (max)
Figure 2. Load current, timing capacitor voltage, and output voltage of the UCC3915 under fault conditions.
SAFETY RECOMMENDATIONS
Although the UCC3915 is designed to provide system protection for all fault conditions, all integrated circuits can ultimately fail short. For this reason, if the UCC3915 is intended for use in safety critical applications where UL or some other safety rating is required, a redundant
UNITRODE CORPORATION 7 CONTINENTAL BLVD. * MERRIMACK, NH 03054 TEL. 603-424-2410 * FAX 603-424-3460
safety device such as a fuse should be placed in series with the device. The UCC3915 will prevent the fuse from blowing for virtually all fault conditions, increasing system reliability and reducing maintenance cost, in addition to providing the hot swap benefits of the device.
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Copyright (c) 2000, Texas Instruments Incorporated

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