The TL497A incorporates all the active functions required in the construction of switching voltage regulators. It also can be used as the control element to drive external components for high-power-output applications. The TL497A was designed for ease of use in step-up, step-down, or voltage-inversion applications requiring high efficiency.

The TL497A is a fixed-on-time variable-frequency switching-voltage-regulator control circuit. The switch-on time is programmed by a single external capacitor connected between FREQ CONTROL and GND. This capacitor, C_T, is charged by an internal constant-current generator to a predetermined threshold. The charging current and the threshold vary proportionally with V_CC. Thus, the switch-on time remains constant over the specified range of input voltage (4.5 V to 12 V). Typical on times for various values of C_T are as follows:

TIMING CAPACITOR, CT (pF)	200	250	350	400	500	750	1000	1500	2000
ON TIME (µs)	19	22	26	32	44	56	80	120	180

The output voltage is controlled by an external resistor ladder network (R1 and R2 in Figures 1, 2, and 3) that provides a feedback voltage to the comparator input. This feedback voltage is compared to the reference voltage of 1.2 V (relative to SUBSTRATE) by the high-gain comparator. When the output voltage decays below the value required to maintain 1.2 V at the comparator input, the comparator enables the oscillator circuit, which charges and discharges C_T as described above. The internal pass transistor is driven on during the charging of C_T. The internal transistor can be used directly for switching currents up to 500 mA. Its collector and emitter are uncommitted, and it is current driven to allow operation from the positive supply voltage or ground. An internal Schottky diode matched to the current characteristics of the internal transistor also is available for blocking or commutating purposes. The TL497A also has on-chip current-limit circuitry that senses the peak currents in the switching regulator and protects the inductor against saturation and the pass transistor against overstress. The current limit is adjustable and is programmed by a single sense resistor, R_CL, connected between V_CC and CUR LIM SENS. The current-limit circuitry is activated when 0.7 V is developed across R_CL. External gating is provided by the INHIBIT input. When the INHIBIT input is high, the output is turned off.

Simplicity of design is a primary feature of the TL497A. With only six external components (three resistors, two capacitors, and one inductor), the TL497A operates in numerous voltage-conversion applications (step-up, step-down, invert) with as much as 85% of the source power delivered to the load. The TL497A replaces the TL497 in all applications.

The TL497AC is characterized for operation from 0°C to 70°C. The TL497AI is characterized for operation from -40°C to 85°C.

• High Efficiency . . . 60% or Greater
• Peak Switch Current . . . 500 mA
• Input Current Limit Protection
• TTL-Compatible Inhibit
• Adjustable Output Voltage
• Input Regulation . . . 0.2% Typ
• Output Regulation . . . 0.4% Typ
• Soft Start-Up Capability
• Can be Used in Buck, Boost, and Inverting Configurations

• Vin (Min) (V)
• 4.5
• Vin (Max) (V)
• 12
• Vout (Min) (V)
• -25
• Vout (Max) (V)
• 30
• Switch current limit (Typ) (A)
• 0.5
• Regulated outputs (#)
• 1
• Switching frequency (Max) (kHz)
• 50
• Iq (Typ) (mA)
• 11
• Features
• Enable
• Rating
• Catalog

TL497A的完整型号有：TL497ACD、TL497ACDR、TL497ACN、TL497ACNSR、TL497ACPWR、TL497AID、TL497AIDR、TL497AIN，以下是这些产品的关键参数及官网采购报价：

TL497ACD，工作温度：0 to 70，封装：SOIC (D)-14，包装数量MPQ：50个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网TL497ACD的批量USD价格：.727（1000+）

TL497ACDR，工作温度：0 to 70，封装：SOIC (D)-14，包装数量MPQ：2500个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网TL497ACDR的批量USD价格：.606（1000+）

TL497ACN，工作温度：0 to 70，封装：PDIP (N)-14，包装数量MPQ：25个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：NIPDAU，TI官网TL497ACN的批量USD价格：.697（1000+）

TL497ACNSR，工作温度：0 to 70，封装：SO (NS)-14，包装数量MPQ：2000个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网TL497ACNSR的批量USD价格：.667（1000+）

TL497ACPWR，工作温度：0 to 70，封装：TSSOP (PW)-14，包装数量MPQ：2000个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网TL497ACPWR的批量USD价格：.606（1000+）

TL497AID，工作温度：-40 to 85，封装：SOIC (D)-14，包装数量MPQ：50个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网TL497AID的批量USD价格：.727（1000+）

TL497AIDR，工作温度：-40 to 85，封装：SOIC (D)-14，包装数量MPQ：2500个，MSL 等级/回流焊峰值温度：Level-1-260C-UNLIM，引脚镀层/焊球材料：NIPDAU，TI官网TL497AIDR的批量USD价格：.606（1000+）

TL497AIN，工作温度：-40 to 85，封装：PDIP (N)-14，包装数量MPQ：25个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：NIPDAU，TI官网TL497AIN的批量USD价格：.697（1000+）

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