一,产品概述(General Description)   
         The JTM1485 requires a minimum number of readily available standard external components. Other features include cable compensation  programmable current limit and thermal shutdown. 二.产品特点(Features)

• Wide Input Voltage Range: 8V ～ 30V
• Up to 93% Efficiency
• Programmable Switching Frequency up
• to 500KHz
• No Loop Compensation Required
• CC/CV control
• Programmable CC Current
• Thermal Shutdown
• Available in SOP8-PP Package

三,应用范围 (Applications)
 

1.  Car Charger / Adaptor
    
2. LED Driver
    
3. Pre-Regulator for Linear Regulators
    
4. Distributed Power Systems
    
5. Battery ChargerCar Charger / Adaptor
    
6. LED Driver
    
7. Pre-Regulator for Linear Regulators
    
8. Distributed Power Systems
    
9. Battery Charger

四,产品封装图 (Package)

PIN	NAME	DESCRIPTION
1	FB	Feedback
2	ILIM	CC Current Settng
3	EN	Enable
4	PDRI	PMOS Gate Drive
5	NDRI	NMOS Gate Drive
6	VIN	Input Supply Voltage
7	RT	Frequency setting
8	SW	Switch Node
9	GND	Ground

五,电路原理图


六, 产品PCB
(略)
七.产品BOM  
  (略)
八.产品PDF文档 

JTM1485

九,功能概述

Application Information
 
The JTM1485 operates by a constant frequency, current mode architecture. The output voltage is set
by an external divider returned to the FB pin. An error amplifier compares the divided output voltage with
a reference voltage of 1.21V and adjusts the peak inductor current accordingly.
 
Thermal Protection
The total power dissipation in JTM1485 is limited by a thermal protection circuit. When the device
temperature rises to approximately +160°C, this circuit turns off the output, allowing the IC to cool. The
thermal protection circuit can protect the device from being damaged by overheating in the event of fault
conditions. Continuously running the JTM1485 into thermal shutdown degrades device reliability.
 
Current Limit
 
Current limit detection occurs during the off-time by monitoring the current through the low-side switch
using an external resistor, RLIM. The current limit value is defined by RLIM. If during the off-time the
current in the low-side switch exceeds the user defined current limit value, the next on-time cycle is
immediately terminated. Current sensing is achieved by comparing the voltage across the low side FET
with the voltage across the current limit set resistor RLIM. For example, the current limit value is 4.5A by
the RLIM =100K. The current limit value rises when the set resistor RLIM rises. The maximum output
current is set by RLIM: RLIM (kΩ) = 1500 · IMAX (A) / RDS_PMOS (mΩ).
 
Oscillator Frequency
The JTM1485 oscillator frequency is set by a single external resistor connected between the RT pin and
the GND pin. The resistor should be located very close to the device and connected directly to the pins
of the IC (RT and GND). An internal amplifier holds the RT pin at a fixed voltage typically 0.6V. The
oscillator frequency rises when the resistor RT falls. To determine the timing resistance for a given
switching frequency, use the equation below:
RT(kΩ)= 22000 /fOSC(kHz)
 
Setting Output Voltage
 
The output voltage is set with a resistor divider from the output node to the FB pin. It is recommended to
use divider resistors with 1% tolerance or better. To improve efficiency at very light loads consider using
larger value resistors. If the values are too high the regulator is more susceptible to noise and voltage
errors from the FB input current are noticeable. For most applications, a resistor in the 10kΩ to 1MΩ
range is suggested for R3. R2 is then given by:
R2 = R3 · [(VOUT / VREF) – 1]
where VREF is 1.21V.
 
Output Cable Resistance Compensation
To compensate for resistive voltage drop across the charger's output cable, the JTM1485 integrates a
simple, user-programmable cable voltage drop compensation using the impedance at the FB pin.
Choose the proper feedback resistance values for cable compensation refer to the curve in Figure 1.
The delta VOUT voltage rises when the feedback resistance R3 value rises, use the equation below
十,相关产品

单P沟道低压MOS场效应管
型号	沟道	VDS	VGS	VTH	ID	IDM	RDS(on)	封装	状态	直接替代型号
		(Max)			(Max)		(Max)
JTM2301/A	P沟道	-20V	-10V	-0.7V	-3A	-10A	65mΩ	SOT23	量产	Si2301/AP2301/SI2305/XP152A/
								SOT23-3L		IRLML6401/IRML6402/AO3423
JTM2301B	P沟道	-20V	-12V	-0.7V	-2.8A	-10A	83mΩ	SOT23	量产	Si2301/AP2301/XP152A/
										IRLML6402/AO3423
JTM2301C	P沟道	-12V	-12V	-0.7V	-2.8A	-10A	85mΩ	SOT23	量产	Si2301/AP2301/XP152A/
										IRLML6402/AO3423
JTM2305	P沟道	-20V	-12V	-0.7V	-4.1A	-15A	39mΩ	SOT23	量产	Si2305/AP2305/APM2305/
										IRLML6401/IRML6402/AO3423
JTM2333	P沟道	-12V	-12V	0.32V	6A	20A	30mΩ	SOT23-3L	量产	Si2333/IRLML6302
JTM2341/B	P沟道	-30V	-20V	-1V	-4.2A	-30A	50mΩ	SOT23-3L	量产	WPM2341/Si2341/AO3401
								SOT23		AO3415/IRLML6401/SI2307
JTM3401/B	P沟道	-30V	-20V	-1V	-4.2A	-30A	50mΩ	SOT23-3L	量产	AO3401/AO3415/IRLML6401
								SOT23		/IRLML6402/SI2307
JTM3401C	P沟道	-30V	-20V	-1.6V	-2.5A	-10A	72mΩ	SOT23	量产	AO3401/AO3407/AO3415/
										IRLML6401/IRLML6402/SI2307
JTM3407/B	P沟道	-30V	-20V	-1.5V	-4.2A	-20A	55mΩ	SOT23-3L	量产	AO3407/AO3415/IRLML6401
								SOT23		IRLML6402/SI2307
JTM3413/B	P沟道	-20V	-12V	-0.7V	-2.5A	-10A	118mΩ	SOT23-3L	量产	AO3413
								SOT23
JTM3415E	P沟道	-20V	-10V	-0.65V	-4.0A	-30A	34mΩ	SOT23-3L	量产	AO3415
	带ESD保护
JTM3421/B	P沟道	-30V	-20V	-1V	-4.2A	-30A	50mΩ	SOT23-3L	量产	AO3421/AO3401/AO3415
								SOT23		WPM2341/IRLML6401/SI2307
JTM2319	P沟道	-40V	-20V	-1.5V	-5.3A	-20A	73mΩ	SOT-23-3L	量产	Si2319
JTM2309	P沟道	-60V	-20V	-1.0V	-1.8A	-7A	170mΩ	SOT-23-3L	量产	Si2309
JTM6401	P沟道	-30V	-20V	-1V	-5.0A	-30A	50mΩ	SOT23-6L	量产	AO6401/Si3481/APM2605/AO6405
										Si3455/SI3457/FDC634P/FDC636P
JTM9435	P沟道	-30V	-20V	-1.6V	-5.1A	-20A	48mΩ	SOP8	量产	CEM9435/APM9435/AP9435/
										Si9435/FDS9435/AO4405
JTM9435B	P沟道	-20V	-10V	-0.7V	-5A	-20A	60mΩ	SOP8	量产	CEM9435/APM9435/AP9435/
										Si9435/FDS9435/AO4405
JTM4435	P沟道	-30V	-20V	-1.5V	-9.1A	-50A	15mΩ	SOP8	量产	AO4435/CEM4435/APM4435/
										AP4435/Si4435/FDS4435
JTM4407	P沟道	-30V	-20V	-1.65V	-12A	-60A	14mΩ	SOP8	量产	AO4407/CEM4407/APM4407/
										AP4407/Si4407/FDS4407
JTM4409	P沟道	-30V	-20V	-1.75V	-15A	-80A	8mΩ	SOP8	量产	AO4409/AO4407/AO4435/CEM4435
										APM4435/AP4435/Si4435/FDS4435
JTM4443	P沟道	-40V	-20V	-1.5V	-6A	-24A	73mΩ	SOP8	量产	AO4443
										IRF7241
JTM4485	P沟道	-40V	-20V	-2.0V	-15A	-60A	30mΩ	SOP8	量产	AO4485
										IRF7240
JTM4441	P沟道	-55V	-20V	-2.6V	-5A	-25A	64mΩ	SOP8	量产	AO4441/AO4421/
										AO4443
JTM5853	P沟道+肖特基	22V	8V	0.69V	3A	12A	110mΩ	DFN2*3-8	量产	Si5853/AON4703/NHPD4P02
JTM16P12D	P沟道	12V	12V	0.7V	16A	65A	18mΩ	DNF2*2-6	量产	AON2701/AON2401/3/5/IRLHS2242