MAX1640CSLASHD datasheet(5/12 Pages) MAXIM

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Adjustable-Output, Switch-Mode

Current Source with Synchronous Rectifier

_______________________________________________________________________________________

____________________________Typical Operating Characteristics (continued)

(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)

A: OUTPUT CURRENT, D0 = D1 = 0 1A/div

VIN = 12V, VSET = 1V, RLOAD = 4

Ω, NO OUTPUT CAPACITOR

B: LOAD VOLTAGE, AC coupled, 500mV/div

CURRENT-MODE CHANGE RESPONSE TIME

2ms/div

EXITING OFF MODE

A: D0 = D1 = 1 2V/div

VIN = 12V, RLOAD = 4

B: OUTPUT CURRENT, 0.5A/div

μs/div

______________________________________________________________Pin Description

NAME

FUNCTION

LDOL

Internal, Ground-Referenced Low-Dropout Linear Regulator Output.

Bypass LDOL with a 0.1µF capacitor in parallel with a 4.7µF capacitor to GND.

TOFF

Off-Time Select Input. A resistor (RTOFF) connected from TOFF to GND programs the off-time for the hys-

teretic PWM step-down converter. This resistor also sets the period in duty-cycle mode. See Duty-Cycle

Mode and Programming the Off-Time.

3, 4

D1, D0

Digital Inputs. Select mode of operation (Table 1).

Constant-Current Loop Compensation Input. Bypass CC with a 0.01µF capacitor to GND.

TERM

Maximum Output Voltage Termination Input. When VTERM exceeds the reference voltage, the comparator

resets the internal PWM latch, shutting off the external P-channel FET.

SET

Current Select Input. Program the desired current level by applying a voltage at SET between 0V and VREF,

(I = VSET / 13.3RSENSE). See Figure 2.

REF

Reference Voltage Output (VREF = 2V). Bypass REF with a 0.1µF capacitor to GND.

NDRV

Gate Drive for an optional N-channel FET synchronous rectifier

PGND

High-Current Ground Return for the output drivers

CS+

Positive Current-Sense Comparator Input

CS-

Negative Current-Sense Comparator Input

GND

Ground

PDRV

Gate Drive for the P-channel FET

LDOH

Internal, Input-Referenced Low-Dropout Linear Regulator Output.

Bypass LDOH with a 0.33µF capacitor to IN.

Power-Supply Input. Input of the internal, low-dropout linear regulators.

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