Electronic Components Datasheet Search |
|
UCC1837 Datasheet(PDF) 3 Page - Texas Instruments |
|
UCC1837 Datasheet(HTML) 3 Page - Texas Instruments |
3 / 8 page 3 UCC1837 UCC2837 UCC3837 ELECTRICAL CHARACTERISTICS: Unless otherwise specified, TA = –55°C to 125°C for the UCC1837, –25°C to 85°C for the UCC2837 and 0°C to 70°C for UCC3837; VDD = 5V, CT = 10nF, CCAP = 100nF. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS FET Driver Peak Output Current VCAP = 10V, VOUT = 1V 0.5 1.5 2.5 mA Average Output Current VOUT = 1V 25 100 175 µA Max Output Voltage VDD = 4.5V, IOUT = 0 µA 8.4 9.7 V VDD = 4.5V, IOUT = 10 µA, 0°C to 70°C 8 9 V VDD = 4.5V, IOUT = 10 µA, –55°C to 125°C 7.5 9 V Charge Pump CAP Voltage VDD = 4.5V, C/S = 0V 11 12.5 V VDD = 12V, C/S = 0V 15 16.5 V Note 1: This is defined as the voltage on FB which results in a DC voltage of 8V on VOUT. PIN DESCRIPTIONS CAP: The output of the charge pump circuit. A capacitor is connected between this pin and GND to provide a floating bias voltage for an N-Channel MOSFET gate drive. A minimum of a 0.01 µF ceramic capacitor is rec- ommended. CAP can be directly connected to an exter- nal regulated source such as +12V, in which case the external voltage will be the source for driving the N-Channel MOSFET. COMP: The output of the transconductance error ampli- fier and current sense amplifier. Used for compensating the small signal characteristics of the voltage loop (and current loop when Current Sense Amplifier is active in over curret mode). CS: The negative current sense input signal. This pin should be connected through a low noise path to the low side of the current sense resistor. CT: The input to the duty cycle timer circuit. A capacitor is connected from this pin to GND, setting the maximum ON time of the over current protection circuits. See the Application Section for programming instructions. FB: The inverting terminal of the voltage error amplifier, used to feedback the output voltage for comparison with the internal reference voltage. The nominal DC operating voltage at this pin is 1.5V GND: Ground reference for the device. For accurate out- put voltage regulation, GND should be referenced to the output load ground. VDD: The system input voltage is connected to this point. VDD must be above 3V. VDD also acts as one side of the Current Sense Amplifier and Comparator. VOUT: This pin directly drives the gate of the external N-MOSFET pass element. The typical output impedance of this pin is 6.5k Ω. Topology and General Operation Unitrode Application Note U-152 is a detailed design of a low dropout linear regulator using an N-channel MOSFET as a pass element, and should be used as a guide for understanding the operation of the circuit shown in Fig. 1. Charge Pump Operation The internal charge pump of the UCC3837 is designed to create a voltage equal to 3 times the input VDD voltage at the CAP pin. There is an internal 5V clamp at the input of the charge pump however that insures the voltage at CAP does not exceed the ratings of the IC. This CAP voltage is used to provide gate drive current to the exter- nal pass element as well as bias current to internal sec- tions of the UCC3837 itself. The charge pump output has a typical impedance of 80k Ω and therefore the loading of the IC and the external gate drive reduces the voltage from its ideal level. The UCC3837 can operate in several states including having the error amplifier disabled (shut down), in normal linear regulation mode, and in overdrive mode where the linear regulator is responding to a tran- sient load or line condition. The maximum output voltage available at VOUT is shown in Fig. 2 for these various modes of operation. The charge pump output is designed to supply 10 µAof average current to the load which is typically the MOSFET gate capacitance present at the VOUT pin.The capacitor value used at CAP is chosen to provide holdup APPLICATION INFORMATION |
Similar Part No. - UCC1837 |
|
Similar Description - UCC1837 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |