Datasheet LT1176, LT1176-5 (Analog Devices)

LT1176/LT1176-5 Step-Down Switching Regulator
FEATURES
and all current limit components are included on the chip. The topology is a classic positive buck configuration but n 1.2A Onboard Switch several design innovations allows this device to be used as n 100kHz Switching Frequency a positive-to-negative converter, a negative boost converter, n Excellent Dynamic Behavior and as a flyback converter. The switch output is specified n DIP and Surface Mount Packages to swing below ground. n Only 8mA Quiescent Current The LT1176 uses a true analog multiplier in the feedback n Preset 5V Output Available loop. This makes the device respond nearly instantaneously n Operates Up to 35V Input to input voltage fluctuations and makes loop gain indepen- n Micropower Shutdown Mode dent of input voltage. As a result, dynamic behavior of the regulator is significantly improved over previous designs.
APPLICATIONS
On-chip pulse by pulse current limiting makes the LT1176 nearly bust proof for output overloads or shorts. The input n Buck Converter with Output Voltage Range of 2.5V to 30V voltage range as a buck converter is 8V to 35V, but a self boot feature allows input voltages as low as 5V in the n Positive-to-Negative Converter inverting and boost configurations. n Negative Boost Converter n Multiple Output Buck Converter The LT1176 is available in a low cost 8-lead DIP package with frequency preset at 100kHz and current limit at 1.7A.
DESCRIPTION
An adjustable output is offered as well as a preset 5V ver- sion. For further design details and application help, see The LT®1176 is a 1A monolithic bipolar switching regulator the LT1074/LT1076 data sheet and Application Note 44. which requires only a few external parts for normal opera- L, LT, LTC, LTM, Linear Technology, SwitcherCAD and the Linear logo are registered tion. The power switch, all oscillator and control circuitry trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION Basic 5V Positive Buck Converter 5V Buck Converter Efficiency
L1* 90 100µH L = 100µH ON MAGNETICS INC. 10V T0 35V V 5V, 0.8A SIZE T-50 KOOL Mµ CORE IN VSW LT1176-5 1N5819 VIN = 10V 80 SENSE GND V V C + IN = 20V C1 R3 470µF 2.7k 25V + EFFICIENCY (%) 70 C3 C2 100µF 0.01µF *COILTRONICS #100-1-52 60 11765 TA01 PULSE ENGINEERING, INC. #PE-92102 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 HURRICANE #HL-AG210LL LOAD CURRENT (A) THESE ARE LOW COST POWDERED IRON CORES. OPTIMUM EFFICIENCY AND SMALLEST SIZE IS OBTAINED BY USING A LOW LOSS CORE SUCH 11765 TA02 AS MAGNETICS INC. KOOL Mµ. SEE EFFICIENCY GRAPH. 11765fb 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Block Diagram Package Description Revision History Package Description