七,功能概述
Input Capacitor Selection
The input capacitor is chosen based on the voltage rating and the RMS current rating. For reliable operation, select
the capacitor voltage rating to be at least 1.3 times higher than the maximum input voltage. The maximum RMS
current rating requirement is approximately IOUT/2, where IOUT is the load current. During power up, the input capaci-
tors have to handle large amount of surge current. In low-duty notebook appliactions, ceramic capacitors are
remmended. The capacitors must be connected between the drain of high-side MOSFET and the source of low-
side MOSFET with very low-impeadance PCB layout.
 
MOSFET Selection
The application for a notebook battery with a maximum volt-age of 24V, at least a minimum 30V MOSFETs should
be used. The design has to trade off the gate charge with the RDS(ON) of the MOSFET:
· For the low-side MOSFET, before it is turned on, the body diode has been conducted. The low-side MOSFET
driver will not charge the miller capacitor of this MOSFET.
In the turning off process of the low-side MOSFET,the load current will shift to the body diode first. The
high dv/dt of the phase node voltage will charge the miller capacitor through the low-side MOSFET driver
sinking current path. This results in much less switching loss of the low-side MOSFETs. The duty
cycle is often very small in high battery voltage applications, and the low-side MOSFET will con-
duct most of the switching cycle; therefore, the less the RDS(ON) of the low-side MOSFET, the less the power
loss. The gate charge for this MOSFET is usually a secondary consideration. The high-side MOSFET
does not have this zero voltage switching condition, and because it conducts for less time
compared to the low-side MOSFET, the switching loss tends to be dominant. Priority should be given
to the MOSFETs with less gate charge, so that both the gate driver loss and switching loss will be minimized.
The selection of the N-channel power MOSFETs are de-termined by the RDS(ON), reversing transfer capacitance
Layout Consideration
In any high switching frequency converter, a correct layout is important to ensure proper operation of the regulator.
With power devices switching at higher frequency, the resulting current transient will cause voltage spike across
the interconnecting impedance and parasitic circuit elements. As an example, consider the turn-off transition
of the PWM MOSFET. Before turn-off condition, the MOSFET is carrying the full load current. During turn-off,
current stops flowing in the MOSFET and is freewheeling by the lower MOSFET and parasitic diode. Any parasitic
inductance of the circuit generates a large voltage spike during the switching interval. In general, using short and
wide printed circuit traces should minimize interconnect-ing impedances and the magnitude of voltage spike. And
signal and power grounds are to be kept separating and finally combined to use the ground plane construction or
single point grounding. The best tie-point between the signal ground and the power ground is at the negative
side of the output capacitor on each channel, where there is less noise. Noisy traces beneath the IC are not
recommended. Below is a checklist for your layout:

八,相关产品

Part_No	Package & Pins	Topology	Architecture	Phase	No. of PWM Outputs	Output Current (max)(A)	Input Voltage (V)		Reference Voltage(V)	Bias Voltage (typ) (V)	Quiescent Current (typ)(uA)
							min	max
JTMA7068	SOP-14	Buck	VM	1	1	30	2.9	13.2	0.9	12	8000
	QSOP-16
	QFN4x4-16
JTMA7065	SOP-8	Buck	VM	1	1	20	2.9	13.2	0.8	12	5000
JTMA7065C	SOP-8	Buck	VM	1	1	20	2.9	13.2	0.8	12	5000
JTMA7098	QFN4x4-24	Multiphase	VM	2	1	60	3.1	13.2	0.6	12	5000
JTMA7120	SOP-8	Buck	VM	1	1	20	2.2	13.2	0.8	5月12日	2100
JTMA7120A	SOP-8	Buck	VM	1	1	20	2.2	13.2	0.8	5月12日	2100
JTMA7037/A/B	SOP-8	Buck	VM	1	1	5	5	13.2	1.25 / 0.8	5月12日	3000
	TSSOP-8
JTMA7057	SOP-8	Buck	VM	1	1	10	3.3	5.5	0.8	5	2100
JTMA7062B	SOP-14	Buck	VM	1	1	10	5	13.2	0.8	12	2000
JTMA7066	TSSOP-24	Buck	VM	1	2	20	5	13.2	0.6	5月12日	4000
	QFN5x5-32
JTMA7067N	SOP-14	Buck	VM	1	1	30	2.9	13.2	0.9	12	4000
	QSOP-16
	QFN-16
JTMA7073	SOP-14	Buck	VM	1	1	30	2.2	13.2	0.6	12	5000
JTMA7073A	SOP-14	Buck	VM	1	1	30	2.2	13.2	0.6	12	5000
JTMA7074	SOP-14	Buck	VM	1	1	25	2.2	13.2	0.8	12	5000
JTMA7095/A	LQFP7x7-48	Buck	VM	1	6	0.015	1.4	6.5	-	5	1800
	TQFN7x7-48	Boost
		Flyback
JTMA7116	TSSOP-24P	Buck	VM	1	2	20	2.97	5.5	0.8	5月12日	5000
JTMA7063	SOP-14	Buck	VM	1	1	10	5	13.2	0.8	12	3000
JTMA7064	SOP-8-P	Buck	VM	1	1	30	2.9	13.2	1.2	12	3000
	DIP-8
JTMA7108	SSOP-28	Buck	VM	1	2	20	5	24	0.9	5	1200
	QFN4x4-24
JTMA7158	SOP-20	Buck	VM	1	2	20	2.2	13.2	0.6	5月12日	4000
JTMA7181	SOP-8		VM	1	2	-	-	-	-	5月12日	550
	DFN3x3-10
JTMA38HC/42/3/4/5A	DIP-8	Buck	VM	1	1	1	1.2	9	24	5	9 ~ 24
	SOP-8	Boost
		Flyback
		Forward
JTMA7138	SSOP-16	Buck	VM	1	1	25	3	25	0.6	5	1700
	QFN4x4-16
	TQFN3x3-16
JTMA7199	TDFN3x3-10	Buck	COT	1	1	25	3	25	0.5	5	350
JTMA8700	QFN4x4-24	Buck	CM	2	1	40	4.5	13.2	0.6	5月12日	4000
JTMA8720B	SOP8-P	Buck	VM	1	1	20	3	13.2	0.8	5月12日	2500
	TDFN3x3-10
JTMA8722A/B/C/D	SOP8-P	Buck	VM	1	1	25	3	13.2	0.6 /0.8	5月12日	1200
JTMA8723	TDFN3x3-10	Buck	VM	1	1	25	4	13.2	0.8	5月12日	2000
JTMA8724	TDFN3x3-10	Buck	COT	1	1	25	4.5	25	0.6	5月12日	80
JTMA8725/A	SOP-8P	Buck	VM	1	1	25	4.5	13.2	0.8	5月12日	16000
JTMA8726	TQFN3x3-10	Buck	VM	1	1	25	4.5	13.2	0.6	5月12日	2500
JTMA8727/L	TDFN3x3-10	Buck	COT	1	1	30	3	25	0.8	5月12日	2000
JTMA8728	TQFN3x3-16	Buck	COT	1	1	30	1.8	28	0.6	5	600
JTMA8732	QFN4x4-24	Buck	VM	2	1	50	4.5	13.2	0.6	5月12日	5000
JTMA8811	TQFN4x4-24	Buck	COT	1	2	15	6	25	2	N	550
JTMA8812	TQFN4x4-24	Buck	COT	1	2	15	6	25	2	N	550
JTMA8813/A	TQFN4x4-24	Buck	COT	1	2	20	3	28	0.75	5	800
	TQFN3x3-20
JTMA8814	TQFN3x3-16	Buck	COT	1	1	20	1.8	28	0.75	5	400
JTMA8815	QFN3.5x3.5-14	Buck	COT	1	1	20	1.8	28	0.75	5	400
	TQFN3x3-16
JTMA8816	TQFN3x3-16	Buck	COT	1	2	20	1.8	28	0.75	5	400
JTMA8819	QFN3x3-20	Buck	COT	1	2	20	3	28	1.8 /1.5 /0.5	5	740
	TQFN3x3-16
JTMA8820	TQFN4x4-24	Buck	CM	1	2	15	5	28	0.5	N	3000
	QFN3x3-20
JTMA8821	TDFN3x3-10	Buck	COT	1	1	20	1.8	28	0.5	5	250
JTMA8822/C	TQFN3x3-20	Buck	COT	1	2	15	6	25	2	N	550
JTMA8823A/B	TQFN3x3-20	Buck	COT	1	2	15	5.5	25	0.6	N	50
JTMA8868	TQFN3x3-20	Buck	COT	1	2	20	3	28	0.75	5	180
JTMA7088	QFN4x4-24	Multiphase	VM	2	1	60	3.1	13.2	0.85	12	5000
JTMA7165A/B/C	SOP-8P	Buck	VM	1	1	20	2.9	13.2	0.8	12	16000
JTMA7159A	SOP-20	Buck	VM	2	2	30	10	13.2	1	12	5000
JTMA8828	TDFN3x3-10	Buck	COT	1	1	25	1.8	28	0.7	5	250
JTMA8728	TQFN 3x3 16	Buck	COT	1	1	30	1.8	28	0.6	5	600