ams Datasheet Page 15
[v2-23] 2016-Mar-30 Document Feedback
AS3685A/AS3685B − Detailed Description
Figure 23:
Internal Circuit Diagram of AS3685A/AS3685B
Low Noise Charge Pump
The AS3685 charge pump uses two external flying capacitors
to generate output voltages higher than the battery voltage.
The charge pump can operate in three different modes:
• 1:1 Bypass Mode or Off Mode
• Battery input and output are connected by a
low-impedance switch
• Battery current = output current
• 1:1.5 Mode
• The output voltage is 1.5 times the battery voltage
(without load)
• Battery current = 1.5 times output current
• 1:2 Mode
• The output voltage is 2 times the battery voltage
(without load)
• Battery current = 2 times output current
The flying capacitors are switched at the fixed frequency fclk.
C1+ C1- C2+ C2-
VCP
ILED
ISET
VBAT
EN1
EN2
VBAT
EN1
EN2
TXMask
Low Noise
Charge Pump
1:1, 1:1.5, 1:2 Modes
Digital
Control
1.3V
Vswitch
mode
5.3V
soft_limit
AS3685
Different Control Logic
for AS3685A and AS3685B
1MHz
clk
Overtemp
Detect
VSS
