MAX1965TEEP Maxim Integrated, MAX1965TEEP Datasheet - Page 17

• Manufacturer Part Number: MAX1965TEEP
• Description: Current & Power Monitors & Regulators
• Manufacturer: Maxim Integrated

Find a low-loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite
cores are often the best choice, although powdered
iron is inexpensive and can work well at 200kHz. The
chosen inductor’s saturation rating must exceed the
peak inductor current:
The minimum current-limit threshold must be high
enough to support the maximum load current at the
minimum tolerance level of the current-limit circuit. The
valley of the inductor current occurs at I
minus half of the ripple current:
where R
MOSFET (N
mum current-limit threshold is 190mV (for the typical
250mV default setting). Use the worst-case maximum
value for R
add some margin for the rise in R
Figure 4. Adjustable Output Voltage
V
VALLEY LOW
R
I
DS ON
DS(ON)
PEAK
DS(ON)
(
L
(
). For the MAX1964/MAX1965, the mini-
)
=
I
LOAD MAX
is the on-resistance of the low-side
)
from the MOSFET N
______________________________________________________________________________________
>
I
LOAD MAX
(
Tracking/Sequencing Triple/Quintuple
(
)
+
Setting the Current Limit
* FOR OUTPUT VOLTAGES > 5V, SEE "OUTPUT VOLTAGE SELECTION."



C
COMP1
LIR
)
2
−
DS(ON)






LIR
I
LOAD MAX
2
C2
L
C1
R
C



COMP
COMP2
data sheet, and
I
LOAD MAX
R
(
POK
over tempera-
LOAD(MAX)
(
)
IN
VL
ILIM
POK
COMP
)
MAX1964
MAX1965
Power-Supply Controllers
D1
GND
OUT
BST
DH
LX
DL
FB
ture. A good general rule is to allow 0.5% additional
resistance for each °C of the MOSFET junction temper-
ature rise.
Connect ILIM to VL for the default 250mV (typ) current-
limit threshold. For an adjustable threshold, connect a
resistive-divider from VL to ILIM to GND. The external
adjustment range of 500mV to 2.5V corresponds to a
current-limit threshold of 106mV to 530mV. When
adjusting the current limit, use 1% tolerance resistors
and a 10µA divider current to prevent a significant
increase in the current-limit tolerance.
The MAX1964/MAX1965’s step-down controller drives
two external logic-level N-channel MOSFETs as the cir-
cuit switch elements. The key selection parameters are:
1. On-resistance (R
2. Maximum drain-to-source voltage (V
3. Minimum threshold voltage (V
4. Total gate charge (Q
5. Reverse transfer capacitance (C
The high-side N-channel MOSFET must be a logic-level
type with guaranteed on-resistance specifications at
V
tance (R
GS
C
BST
≤ 4.5V. Select the high-side MOSFET’s on-resis-
N
N
DS(ON)
H
L
L
C
IN
INPUT
4.5V TO 28V
) so I
R1
R2
DS(ON)
PEAK
OUTPUT
1.25V TO 5V*
C
g
OUT
)
✕
)
R
DS(ON)
TH(MIN)
MOSFET Selection
RSS
≤ 225mV for the
)
DS(MAX)
)
)
17