LT1107 Linear Technology, LT1107 Datasheet
LT1107
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LT1107 Summary of contents
Page 1
... The device requires only three external components to deliver a fixed output 12V. Supply voltage ranges from 2V to 12V in step-up mode and to 30V in step-down mode. The LT1107 functions equally well in step-up, step- down, or inverting applications. The LT1107 is pin-for-pin compatible with the LT1111, but has a duty cycle of 70%, resulting in increased output current in many applications ...
Page 2
... Gain Block Output Low OL Reference Line Regulation Maximum Switch Current ...................................... 1.5A Operating Temperature Range LT1107C ................................................ LT1107M ........................................ – 125 C Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 ORDER PART NUMBER I 1 LIM LT1107CN8 ...
Page 3
... – 400 – 350 mV LT1107M MIN TYP MAX UNITS 500 kHz 0.2 0.4 %/V 0.8 %/V 0.5 0.65 V 0.5 0.65 V 1.5 V 2.0 V LT1107C MIN TYP MAX UNITS 450 kHz 13 12.0 s 0.2 0.7 %/V 0.5 0.65 V 1.1 1 ...
Page 4
... LT1107 W U TYPICAL PERFOR A Saturation Voltage, Step-Up Mode (SW2 Pin Grounded) 1 0.6 0.4 0 0.2 0.4 0.6 0.8 1.0 1.2 SWITCH CURRENT (A) 1107 G01 Quiescent Current 400 350 300 250 200 150 100 –55 –35 – 105 125 TEMPERATURE (°C) 1107 G05 Switch ON Time ...
Page 5
... SET (Pin 7): GB Input amp with positive input connected to SET pin and negative input connected to 1.25V reference. FB/SENSE (Pin 8): On the LT1107 (adjustable), this pin goes to the comparator input. On the LT1107-5 and LT1107-12, this pin goes to the internal application resistor that sets output voltage. Duty Cycle Step-Down Mode 70 ...
Page 6
... V and the emitter drives the inductor. The LT1107-5 and LT1107-12 are functionally identical to the LT1107. The -5 and -12 versions have on-chip voltage setting resistors for fixed 5V or 12V outputs. Pin 8 on the fixed versions should be connected to the output. No external resistors are needed ...
Page 7
... These equations assume that inductor current is zero. This situation is called “discon- tinuous mode operation” in switching regulator parlance. Setting “t” to the switch ON time from the LT1107 speci- fication table (typically 11 s) will yield I “L” and V . Once I ...
Page 8
... LT1107 PPLICATI S I FOR ATIO where DC = duty cycle (0.50 in step-down mode switch drop in step-down mode diode drop (0.5V for a 1N5818 output current OUT V = output voltage OUT V = minimum input voltage actually a function of switch current which is in turn SW a function of V ...
Page 9
... PPLICATI S I FOR ATIO A The usual step-up configuration for the LT1107 is shown in Figure 1. The LT1107 first pulls SW1 low causing appear across L1. A current then builds up in L1. CESAT At the end of the switch ON time the current PEAK ...
Page 10
... Figure 4. Negative-to-Positive Converter Using the I Pin LIM The LT1107 switch can be programmed to turn off at a set switch current, a feature not found on competing devices. This enables the input to vary over a wide range without exceeding the maximum switch rating or saturating the inductor. Consider the case where analysis shows the LT1107 must operate at an 800mA peak switch current with a 2V input ...
Page 11
... Using the Gain Block The gain block (GB) on the LT1107 can be used as an error amplifier, low-battery detector or linear post regulator. The gain block itself is a very simple PNP input op amp with an open collector NPN output ...
Page 12
... FAX TELEX 24V-to-5V Step-Down Converter 24V IN 220 V I LIM IN SW1 + LT1107 SENSE GND SW2 150 H* 1N5818 *COILTRONICS CTX150-4 U Dimensions in inches (millimeters) unless otherwise noted. J8 Package, 8-Lead Ceramic DIP (4 PLCS) 0.015 – 0.060 (0.381 – 1.524) 0.045 – 0.068 (1.143 – ...