TL284xB

Features:

· Low Start-Up Current (<0.5 mA)
· Trimmed Oscillator Discharge Current
· Current Mode Operation to 500 kHz
· Automatic Feed-Forward Compensation
· Latching PWM for Cycle-by-Cycle Current Limiting
· Internally Trimmed Reference With Undervoltage Lockout
· High-Current Totem-Pole Output Undervoltage Lockout With Hysteresis
· Double-Pulse Suppression


Pinout




Specifications

			MIN	MAX	UNIT
VCC         Supply voltage	Low impedance source			30	V
	ICC < 30 mA			Self limiting
VI             Analog input voltage range	VFB and ISENSE		0.3	6.3	V
ICC          Supply current				30	mA
IO            Output current				±1	A
IO(sink)   Error amplifier output sink current				10	mA
JA    Package thermal impedance(3) (4)	D package	& pin		97	/W
		14 pin		86
	P package			85
Output energy	Capacitive load			5	J
TJ       Virtual junction temperature				150
Tstg    Storage temperature range			65	150
Tlead   Lead temperature	Soldering, 10 s			300

(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the
     device.  These are stress ratings only, and functional operation of the device at these or any other
     conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure
     to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) All voltages are with respect to the device GND terminal.
(3) Maximum power dissipation is a function of T_J(max), _JA, and T_A. The maximum allowable power dissipation
     at any allowable ambient temperature is P_D = (T_J(max) T_A)/_JA. Operating at the absolute maximum T_J
     of 150 can impact reliability.
(4) The package thermal impedance is calculated in accordance with JESD 51-7.


Description

The TL284xB and TL384xB series of control integrated circuits provide the features that are necessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes, with a minimum number of external components. Internally implemented circuits include an undervoltage lockout (UVLO) and a precision reference that is trimmed for accuracy at the error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation (PWM) comparator that also provides current-limit control, and a totem-pole output stage designed to source or sink high-peak current. The output stage, suitable for driving N-channel MOSFETs, is low when it is in the off state.

The TL284xB and TL384xB series are pin compatible with the standard TL284x and TL384x with the following improvements. The start-up current is specified to be 0.5 mA (max), while the oscillator discharge current is trimmed to 8.3 mA (typ). In addition, during undervoltage lockout conditions, the output has a maximum saturation voltage of 1.2 V while sinking 10 mA (V_CC = 5 V).

Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges. Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842B and TLx844B devices make them ideally suited to off-line applications. The corresponding typical thresholds for the TLx843B and TLx845B devices are 8.4 V (on) and 7.6 V (off). The TLx842B and TLx843B devices can operate to duty cycles approaching 100%. A duty-cycle range of 0% to 50% is obtained by the TLx844B and TLx845B by the addition of an internal toggle flip-flop, which blanks the output off every other clock cycle.The TL284xB-series devices are characterized for operation from 40 to 85. The TL384xB-series devices are characterized for operation from 0 to 70.