The JTMA7142 is a 3A synchronous-rectified Buck converter wi(2)

六.电路原理图

七,功能概述

Thermal Consideration

In most applications, the JTMA7104A does not dissipate much heat due to its high efficiency. But, in applications
where the JTMA7104A is running at high ambient tem perature with low supply voltage and high duty cycles, the
heat dissipated may exceed the maximum junction temperature of the part. If the junction temperature reaches
approximately 150°C, both power switches will be turned off and the SW node will become high impedance.
To avoid the JTMA7104A from exceeding the maximum junction temperature, the user will need to do some ther-
mal analysis. The goal of the thermal analysis is to deter mine whether the power dissipated exceeds the maxi-
mum junction temperature of the part. The power dissipated by the part is approximated:
PD ≅ IOUT2 x (RP-FET x D+RN-FET x (1-D))
The temperature rise is given by:
TR = (PD)(èJA)
Where PD is the power dissipated by the regulator, D is
duty cycle of main switch
D = VOUT/VIN
The èJA is the thermal resistance from the junction of the
die to the ambient temperature. The junction temperature,
TJ, is given by:
TJ = TA + TR
Where TA is the ambient temperature.

Layout Consideration
For all switching power supplies, the layout is an impor tant step in the design; especially at high peak currents
and switching frequencies. If the layout is not carefully done, the regulator might show noise problems and duty
cycle jitter.
1. The input capacitor should be placed close to the VIN and GND. Connecting the capacitor and VIN/GND with
short and wide trace without any via holes for good input voltage filtering. The distance between VIN/GND
to capacitor less than 2mm respectively is recommended.
2. To minimize copper trace connections that can inject noise into the system, the inductor should be placed
as close as possible to the SW pin to minimize the noise coupling into other circuits.
3. The output capacitor should be place closed to converter VOUT and GND.
4. Since the feedback pin and network is a high imped ance circuit the feedback network should be routed
away from the inductor. The feedback pin and feedback network should be shielded with a ground plane
or trace to minimize noise coupling into this circuit.
5. A star ground connection or ground plane minimizes ground shifts and noise is recommended.

八,相关产品

Part_No	Package & Pins	Topology	Architecture	No. of PWM Outputs	Drive Lout (A)	Vin (V)		Fmax(Khz)	Vref (V)	R-Top (milohm)	R-Sync (milohm)	Iq (No load) (uA)
Part_No	Package & Pins	Topology	Architecture	No. of PWM Outputs	Drive Lout (A)	min	max	Fmax(Khz)	Vref (V)	R-Top (milohm)	R-Sync (milohm)	Iq (No load) (uA)
jtma7083	TQFN5x6-28	Buck	CM	1	5	4.5	26	380	0.8	50	20	1000
jtma7085	SOP-8	Buck	CM	1	2	4.5	26	380	0.8	100		1000
jtma7089	SOP-8P	Buck	CM	1	4	4.5	26	380	0.8	80		1000
jtma7104	SOT-23-5	Buck	CM	1	1	2.7	6	1500	0.6	280	250	25
jtma7104	TSOT-23-5	Buck	CM	1	1	2.7	6	1500	0.6	280	250	25
jtma7104A	SOT-23-5	Buck	CM	1	1	2.7	6	1500	0.6	280	250
jtma7142	SOP-8	Buck	CM	1	3	4.3	14	500	0.8	70	70	500
jtma7145	SOP-8P	Buck	CM	1	3	4.3	14	500	0.8	55	45	500
jtma7153B	TDFN3x3-10				3	2.6	5.5	2000	0.8	110	110	460
jtma7176	TDFN3x3-10	Buck	CM	2	1	2.7	6	1500	0.6	280	250	500
jtma7176A	TDFN3x3-10	Buck	CM	2	1	2.7	6	1500	0.6	280	250
jtma7178	TDFN2x2-6	Buck	CM	1	1	2.7	6	1500	0.6	280	250	25
jtma7178A	TDFN2x2-6	Buck	CM	1	1	2.7	6	1500	0.6	280	250
jtma7179	TDFN3x3-12	Buck	CM	2	1	2.7	6	1500	0.6	280	250	25
jtma7179A	TDFN3x3-12	Buck	CM	2	1	2.7	6	1500	0.6	280	250
jtma7290	TDFN2x2-8		CM	1	1	3.3	8	1500	0.6	280	250	25
jtma7300	SOP-8	Buck	CM	1	2	4.5	24	340	0.925	110	110	1900
jtma7301	SOP-8P	Buck	CM	1	3	4.5	24	340	0.925	110	110	1900
jtma7302	SOP-8	Buck	CM	1	2	4.5	24	340	0.92	130	130	1900
jtma7302B	SOP-8P	Buck	CM	1	2	4.5	24	340	0.92	130	130	1900
jtma7303	SOP-8P	Buck	CM	1	3	4.5	24	340	0.92	85	85	1900
jtma7304	SOP-8P	Buck	CM	1	4	4.5	24	340	0.8	85	85	1900
jtma7311	SOP-8P	Buck	CM	1	3	4.5	24	1300	0.925	110	110	1900
jtma7312	SOP-8	Buck	CM	1	2	4.5	24	340	0.925	110	110	1900
jtma7313	SOP-8P	Buck	CM	1	3	4.5	24	340	0.925	110	110	1900
jtma7314	TSOT-23-8	Buck	CM	1	2	4.5	24	500	0.8	150	70	500
jtma7322	SOP-8P	Buck	CM	1	2	2.5	6	1000	0.8	85	75	460
jtma7322	TDFN3x3-10	Buck	CM	1	2	2.5	6	1000	0.8	85	75	460
jtma7323	SOP-8P	Buck	CM	1	3.2	2.5	6	1000	0.8	85	75	460
jtma7323	TDFN3x3-10	Buck	CM	1	3.2	2.5	6	1000	0.8	85	75	460
jtma7324	SOP-8P	Buck	CM	1	4	2.5	6	500	0.8	85	75	460
jtma7324	TDFN3x3-10	Buck	CM	1	4	2.5	6	500	0.8	85	75	460
jtma7325	SOP-8P	Buck	CM	1	5	2.5	6	1000	0.6	65	55	460
jtma7334	SOP-8	Buck	CM	1	2	4.5	24	340	0.8	110	110	1900
jtma7335	SOP-8P	Buck	CM	1	3	4.5	24	340	0.8	110	110	1900
jtma7336	TDFN3x3-10	Buck	CM	1	2	4.5	24	340	0.8	110	110	1900
jtma7337	TDFN3x3-10	Buck	CM	1	3	4.5	24	340	0.8	110	110	1900
jtma8713	TQFN4x4-23	Buck	COT	1	6	2.7	28	100~1000	0.8	30	9	750
jtma8802	TQFN5x6-28	Buck	COT	1	8	3	25	500	0.75	12	12	400
jtma8804	TDFN3x3-10	Buck	CM	1	3	2.6	6	1000	0.6	65	55	460
jtma8805	TDFN3x3-10	Buck	CM	1	3	2.6	6	1000	0.6	75	55	460
jtma8807	TQFN3x3-16	Buck	COT	1	8	6	28	500	0.6	24	14	80
jtma8824	TSOT-23-6	Buck	CM	1	1	2.7	5.5	1500	0.6	280	250	25
jtma8835	TDFN3x3-10	Buck	CM	1	3	4.5	24	600	0.8	70	70	400
jtma7414	TSOT-23-8A	Buck	CM	1	2	4.5	24	500	0.788	150	70	1000
jtma7319	TSOT-23-8A	Buck	CM	1	2.5	4.5	24	500	0.807	140	60	1000
jtma8715	TQFN 4x4 23	Buck	COT	1	6	2.7	28	100~1000	0.8	30	12	700
jtma8716A	TQFN 5x5 30	Buck	COT	1	12	2.7	28	300~1000	0.8	14.6	7.8	750
jtma8715	TQFN 4x4 23	Buck	COT	1	6	2.7	28	100~1000	0.8	30	12	700
jtma8805B	TDFN 3x3 10	Buck	CM	1	3	2.6	6	1000	0.8	75	55	460
jtma8805A	TDFN 3x3 10	Buck	CM	1	3	2.6	6	1000	0.8	75	55	460

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